We're happy to send you the first issue of the Electronic Newsletter of the International Working Group on Larviculture of Fish and Shellfish. It's still suffering from some children's diseases, but in the near future we hope to send it in a more definitive form at least on a monthly basis. Our future email address, larvi@UGent.be is not operational yet, so I suggest that any comments/suggestions/requests are sent, for the time being, to gilbert.vanstappen@UGent.be.
As we are planning to get on WWW in the (near ?) future, we'd like to know if you have access to this means of electronical communication.
Please inform us.
Subscription to the IWGL can be made via the standard form, that can be obtained from the EAS (European Aquaculture Society), Coupure Rechts 168, B-9000 Gent, Belgium, tel. 32-9-2237722, fax 32-9-2237604 (email address not yet available), or from our lab.
Of course this @NL can hardly be viable without the contribution of its readers. Feel free to comment and to communicate.
Regards,
Gilbert Van Stappen
In reply to Will Borgeson's comments (italics)
Most commercial and research hatcheries feed bivalve larvae live
algae cells of species that have been shown to have good nutritive
characteristics (tropical *Isochrysis,* *Chaetoceros* spp, etc.).
I think the most significant nutrition variable for larvae may
well be what is in the egg. A typical pattern for crashing larvae is
that they survive well to straight-hinge, then crash, apparently unable
to feed on the *ad libitum* ration of live algae that is provided. Other
times the crash happens later; around 10 days post-fert is not uncommon.
This 10-day crash often involves just a percentage of the larvae.
Other times the major mortality is delayed until metamorphosis.
A group of researchers in Tasmania did some work about ten years ago which
showed a positive correlation between bacterial levels in algal cultures
(tropical *Isochrysis,* *Chaetoceros* spp, etc.) fed to Pacific oyster
larvae (in a commercial hatchery) and crashes. (Lewis et al. 1988
Aquaculture 69: 241-251).
We found that algal cultures "seemed" to be safe until culturable bacterial
counts exceeded ~2 x 10^6/mL, then any amount of said cultures fed to
larvae (at any time during the larval cycle) resulted in mortalities within
days.
Similar circumstances of bacteriologically -unsafe algal cultures could
also explain the crashes mentioned by Will.
Tom Lewis
Another interesting bit of info from a Tasmanian study
found that oyster larvae cultured in .2 micron filtered water crashed,
while controls grown in roughly filtered water thrived. Seems one can
get things too clean, as well as too dirty. Apparently the few bacteria
that came in with the zygotes found the clean water plus nutrient
situation to be like a blank agar plate. I don't have that ref. in front
of me now, but it may well have been Tom's work. In any case it was a
good and fascinating paper.
Unfortunately we don't have a pathology group set up to do the
plating work to routinely test our algae for bacteria. I pasteurize the
water that will be used for the algae, and rarely have an algae crash;
have had none at all this year. But that doesn't mean there aren't
bacteria in there. I do tend to tweak thru algae cultures rapidly, they
aren't hanging around a long time for bacteria to proliferate. But I
would like to be examining this. Still, our bivalve larval survivorship
seems closely linked with the gonad cycle of the parents, especially the
mothers.
My gut feeling is that bivalve larvae can handle having some
bacteria around, as long as there are enough competing microbes to keep
each other in balance. There has been much work that indicates that there
is a distinct seasonality to oyster bivalve success. The gametes need to
be optimal to get optimal survival...weak larvae can't feed well, and
probably have compromised immune systems, making it difficult for them to
deal with bacteria that may well be ubiquitous.
I'll check out Tom's paper mentioned above when I get a chance,
but I'm wondering how long it usually takes to get up to that number of
bacterial colonies...
Further to Will's latest message:
No it wasn't my paper, but by the same group:
Our work was done using algae cultured on a semi-continuous basis. i.e.
10-50% of the algae culture was drained fom the algal culture bags, and the
bags refilled with fresh culture medium. Is this similar to your work Will?
The hatchery in which we did this work was pastueriseng algae water when I
first arrived. The pasteurised culture medium routinely had bacterial
levels around 10^4 by the time the water had cooled enough for
inocculation. Yuk!!
We quickly moved to 0.2um filtering for similar reasons to those Will
expressed earlier. i.e. it's best to provide some "natural" bacteria in the
culture medium to prevent opportunisitic contaminants getting an unimpeded
chance to grow in the cultures. In this case the 0.2um filtration gear
gave us ~50 bacteria/100ml at the time of inocculation.
When using the original and (admittedly) poorly designed pasteurisation
facility, algal cultures were achieving bacterial counts in the order of
10^6 to 10^7 within 3-5 days of inocculation, with most (>90%) cultures
exceeding 2 x 10^6 bact/ml during their harvest life.
Once the 0.2um filtration system was correctly installed, most algal
cultures reached around 10^5 to 10^6 bact/ml within 4-6 days and rarely
(<10%) exceeded 2 x 10^6 bact/ml during their harvest life.
Obviously, the level of larval survivorship will be determined by a
combination of many factors, including genetics, water quality and bacteria
in feed algae, but I thought I'd drop in my few cents worth to this
discussion.
This is in response to your request for information on cod
farming. I am a graduate student in the Master of Aquaculture program
at Simon Fraser University, Burnaby, B.C. I have domee a fairly
extensive literature search on cod aquaculture myself and here are
some references that may be of interest to you.
It's an awesome task to attempt to summarise such a multifaceted
meeting in just a few minutes but in doing so I must emphasise that I am the
front man for the combined efforts of Prof Tom Lam (Department of Zoology,
University of Singapore) and myself. I also acknowledge the helpful comments
of other participants.
We were asked to highlight advances made since Larvi '91 and to
identify, where appropriate, perceived deficiencies in our coverage of the
subject area. With regard to advances, I think it has to be said that at
this stage in the development of the field of aquaculture quantum leaps
forward can not be expected, rather we are seeking a steady step-wise erosion of
the problems that confront us.
The first two days of the meeting were dedicated to the subjects
which most concern culturists, namely egg quality and the availability and
quality of food. With regard to the former we learned there has been some
progress in relation to our ability to identify practical criteria for
recognising poor quality eggs as well as in understanding the importance of
hormones in controlling over-ripening and subsequent embryonic and larval
development.
Evidence was presented that mollusc investigators are ahead of the rest of
us in understanding parental influences on egg and larval
development. We also heard that cryopreservation techniques for fish and mollusc
gametes are at or near the point of commercial exploitation.
With regard to nutrition studies it is clear that our thoughts
are still dominated by lipids. The HUFA story does seem to have become the
soap opera of larvae culture - a never-ending tale with a plot that thickens
only very slowly! Much of current work is repetitious or, to put it more
kindly, confirmatory, though some increase in our understanding of
requirements was evident. Since Larvi '91 the focus of attention has moved from
a consideration of total or individual HUFAs to a greater
appreciation of the importance of ratios, not only between DHA and EPA but also with
arachidonic acid and possibly with saturates. In addition, the protective
role of phospholipids has also been appreciated. It does seem we are
moving towards a better understanding of how respective pathways may be
interlinked, but in general the physiological and biochemical mechanisms are still
unclear and important fundamental questions remain unanswered. These include:
The session on the availability of food stressed the importance
of reducing our dependence on Artemia in the light of the current world
shortage of cysts, and in this respect it was encouraging to hear that some
progress toward the development of microdiets both as a partial or total
replacement for live foods has been made. It would, however, be premature to
throw out our Artemia hatching apparatus!
Subsequent sessions on culture techniques and new species gave
us some encouraging snapshots of impressive commercial developments and
new species that will be coming on line, some sooner and others clearly
later. The scale and diversity of recent developments in Taiwan was particularly
impressive. Perhaps our enthusiasm for new species was a little dampened by
the view expressed by Prof Anderson (University of Rhode Island) at an
Economics Workshop that ultimately product diversity will be accomplished
not by increasing the number of species but by devising a variety of
ways of presenting a relatively small number of species to the market.
It was perhaps appropriate that microbiology and disease was left
to the final session since disease is the last thing that a culturist
wants to be reminded about! The importance of the subject, however, is
clearly evident as were the various contributions that probionts can make through
competitive exclusion of pathogens, stimulation of the immune system and the
provision of nutrients as part of the intestinal flora. Subsequent
contributions elaborated on alternative ways of stimulating the non-specific
immune system using substances such as glucans and mannuronic acid. This is
clearly a most important research field that will undoubtedly contribute much
in the future.
Finally, an appeal not to neglect other areas of importance to the
development of culture techniques which have not been prominent
at this meeting. These would include studies of the behaviour and
environmental requirements of target species as well as perhaps the greater use
of genetic and microbiological techniques.
In summary, given that communication is the essence of science,
I would say that this has been a most successful conference. We should all
be grateful to Patrick Sorgeloos, his organising committee and all those who
have provided us with this opportunity to exchange our information and
views in such pleasant surroundings. The organisation has been impeccable
and I do thank and congratulate you for your efforts on our behalf.
B. R. Howell
On behalf of Gidon and myself, firstly I would like to thank
Patrick and the committee for inviting us to give our opinions on behalf
of the private sector and to add our congratulations to those already
voiced by Bari on the usual high standard of organisation and
presentation shown at this conference. Not many of us start a days work
with a classical music interlude, more usually it is to the sounds of
telephones and transistor radios down on the farm. Many thanks and much
appreciated.
We have tried as much as possible even the last few days to
collate the feelings and opinions of our colleagues and I hope that my
comments will reflect most of their views as well as our own.
Concerning the quality of the posters and presentations and
without singling out any single piece of work we were all impressed and
informed on presentations reviewing several relevant topics. In particular:
On the slightly critical side, we would have to add that some of the work
presented seemed to be repetitive and "old hat" and I wonder if some
researchers carry out literature searches before say 1985 when there was a
lot of good ground work done for example on larval rearing using green water
techniques notably by people like Barry and Ed Hoode.
On the positive side we would like to make some suggestions as to the future
organisation of the conference but we realise we are a minority and these are
merely ideas to be bounced around.
Thank you for your attention.
Dear all,
Following the recent discussion on laval metamorphosis/genetics/bacteria
etc I've had a number of requests for copies of our, and I emphasise
**non-peer-reviewed and maybe somewhat dated**, Manual of Hygiene in
Shellfish Hatcheries 45pp, (1986). I don't want to sound like I'm pushing
this manual, but it seems as though some folk may like to have a look at
it.
I have only 2 copies left at present, but am happy to get a few more
printed/photocopied (probably the latter if that's OK) if there is some
interest, and I'd like to get it all done in one hit. I'll have to charge
something for these copies to cover costs, as the original 1984-86 grant
money has definitely run out :-). Probably in the order of Aust$10-15
depending on copying and posting costs (incl P&P).
If anyone else is interested, please let me know directly and I'll get
moving on it.
The mysterious disease hit about 7,060 hectares of land in East
and west Godavari and Krishna districts along the east coast of
India, destroying 1,686 tonnes of shrimp, according to official
estimates. There was also a recurrence of the outbreak earlier
this summer. Though a detailed report was not available,
examination of a few samples by pathologist professor Donald
Lightner of Arizona University, suggested that the cause was
'China virus'. The unauthorised import of shrimp larvae from
where the disease was known to exist is said to be a possible
cause of the outbreak.
(excerpt from article in Seafood International, September 1995)
Bioresource Technology, 51 (1995):265-267
Abstract :
Three different Artemia strains (Belgian, USA and Tuticorin) were
tested for their culture potential when offered five different
diets comprising cabbage leaves, cow dung, poultry manure and pig
dung in varying proportions at 45,60, 75 and 100 ppt salinities.
One mixture of the ingredients gave the best results among the
five diets tested, while the optimum salinity was found to be 75
ppt. Among the three strains the Tuticorin strain gave the best
results.
(excerpt from article in NAGA, ICLARM QUARTERLY Vol 18, No 2)
The manual has been designed to fill the gap in shrimp and
freshwater prawn hatchery information. It gives information on
project formulation, designing, appraisal and implementation of
hatchery projects.
Contents :
Background; Biology of
penaeid shrimps related to hatchery operations; larval
development; hatchery system; hatchery types; site selection
criteria; hatchery design and components; hatchery opreation and
management; do's and don'ts of hatchery management; economics of
shrimp hatchery.
Introduction; life cycle; larval rearing systems; designing of
hatchery; hatchery operation; Model economics.
To add to the thread on larval mortalities and bacteria in various systems...
A grad student from Northeastern University analyzed our seawater, larval,
and algal systems for Vibrio and total viable bacteria a couple of years ago.
At the time we were having high losses in larval cultures of C. virginica.
Our filtration system for larvae consisted of a rapid sand filter for
primary filtration followed by charcoal, and a 20um nominal cartridge filter
and finally- a diatomaceous earth filter and UV treatment before filling
larval tanks.
The student found that bacteria counts (for both vibrio type and general)
typically rose an order of magnitude higher from bulk water after passing
through the filters. UV was effective in reducing vib and total counts 80 to
95%, and there was seasonal variation (positive correlation with
temperature) of both vibrios and totals. She found no direct evidence that
Vibrio type bacteria were suppressed by non-vibrio background levels.
Nontheless -we were still experiencing losses even with the UV treatment.
After numerous experiments- bypassing certain filters, UV- non UV treatment
etc.... we ripped out the entire filtration system and switched to a two
stage filter bag system (25-50um primary and 1um point of use) and have had
excellent survival ever since. Having a filtration system that allowed
colonization of bacteria and reducing bacteria levels to too low a
concentration apparently both played a role in poor larval survival. A good
example of KISS I guess (Keep it simple...)
I also agree that too high a concentration of even background bacteria is a
bad thing- but I'm wondering about Tom Lewis's number of app 2x10^6/ml. Our
student found that epifluorescence counts were usually two orders of
magnitude higher than plate (viable) counts. Is the 2E+06 based on plating?
Scott Feindel
In reply to Will Borgeson's comments (italics)
Most commercial and research hatcheries feed bivalve larvae live
algae cells of species that have been shown to have good nutritive
characteristics (tropical *Isochrysis,* *Chaetoceros* spp, etc.).
I think the most significant nutrition variable for larvae may
well be what is in the egg. A typical pattern for crashing larvae is
that they survive well to straight-hinge, then crash, apparently unable
to feed on the *ad libitum* ration of live algae that is provided. Other
times the crash happens later; around 10 days post-fert is not uncommon.
This 10-day crash often involves just a percentage of the larvae.
Other times the major mortality is delayed until metamorphosis.
A group of researchers in Tasmania did some work about ten years ago which
showed a positive correlation between bacterial levels in algal cultures
(tropical *Isochrysis,* *Chaetoceros* spp, etc.) fed to Pacific oyster
larvae (in a commercial hatchery) and crashes. (Lewis et al. 1988
Aquaculture 69: 241-251).
We found that algal cultures "seemed" to be safe until culturable bacterial
counts exceeded ~2 x 10^6/mL, then any amount of said cultures fed to
larvae (at any time during the larval cycle) resulted in mortalities within
days.
Similar circumstances of bacteriologically -unsafe algal cultures could
also explain the crashes mentioned by Will.
I've had a chance to read the paper Tom referred to on this
subject, and on which he was major author. A good piece of work!
A couple of comments:
A final note - in Tom's study larvae started out at 16 d-stage
per ml. In part due to advice from commercial hatchery personnel and in
part due to our own observations, we feel that, at least in static
cultures, this is a bit high. We start at 5/ml and usually end up with
around 1/ml worth of spat. This varies greatly however depending on
genetic group, degree of inbreeding, season, etc.
In reply to Daniel E. Gruenberg (italics)
Will,
Could you please explain to me why you chose to pasteurize the water
instead of using more typical techniques for creating sterile water? With
milk the reason for pasteurization is to try to preserve certain
nutritional factors and protein structures. Is there someting you are
trying to protect in the water.
I apologize if this is an ignorant question, but larviculture is not my
specialty.
Not at all Daniel. Some years ago I had been having periodic
problems with contamination and resultant algal crashes; *Paramecium*-like
protozoans were usually responsible. I had been using nominal 1 micron
filtration and UV to prep the seawater for algal culture.
In setting up a hatchery for larviculture, I chose a plate/frame
heat exchanger to bring the seawater up to 25 C for water changes. In
the face of the recurrent algal crashes, I decided to see how hot the
exchanger could get seawater. It brought it to 70-80 C with reasonable
flow. This led me to try this water, once cooled, for algae culture. It
worked extremely well, and I've been using it ever since.
I also tried .2 micron filtration. This also worked very well,
but the filter cartridges I was using were very expensive, needed to be
backflushed with water that also needed to be submicron filtered, and
only let me know if they were blown out when contamination again
occurred. The pasteurization technique is far more reliable and
virtually free. I do however look forward to hearing more about Tom's
filtration setup.
In answer to your question re: protection, I'm protecting the
algae cultures, and perhaps selecting for certain bacteria. I'm aware
that some bacteria are getting through, just as some bacteria survive
milk pasteurization.
The heating no doubt does things to the seawater chemistry (as
does UV, bleach/debleach). It just kills all the protozoans that eat
algae. I'm now intrigued by Tom's work re: bacteria, and may find a way
to more closely examining what pasteurization is doing to them. It's
interesting to note that even the .2 micron filtration allows some
bacteria to pass.
I would just like to echo Will's comments of UV/Chlor-dechlor and
pasteurization for phytoplankton culture.
I also have had problems w/ UV and found that while it
may kill some or most- you never get all, and you do leave a nice enrichment
that is out of balance in terms of microbial ecology- in my experience
often leading to a bloom of vibrios.
Chlorination leaves chlorinated organics if you have any organics (who
doesn't) and if you have nitrate you can even generate toxic levels of
nitrosamine. (algae don't seem to mind, but bivalve lavae do)
I have tried all three and had strongest algal cultures w/ pasteurization.
Pasteurization may even be preferable to autoclaving because certain
metals will precipitate or form bizare complexes at higher temperatures.
Also- for large batch or semi-continuous algal cultures I have had good
sucess w/ 0.2um FSW. Filter costs and success vary greatly w/ manufacturer
and real porosity of cartridge.
One last observation- Healthy algal cultures are usually nearly bacteria
free in my experience. I would not say axenic, because I know my stock
cultures were contaminated w/ many different bacteria. However, once up
in significant numbers in a large healthy culture, I could never plate
anything out! If I did, it usually preceeded a crash in the algal culture.
I would love to see an equipment supplier come out with a plate heat
exchanger to heat the water up and hook it up to a counter current heat
exchanger to both take advantage of the waste heat in the
post-pasteurized SW in heating up incomming SW and to speed up cooling off the
pasteurized SW so that it could be used sooner.
Bob Rheault
I already have the two heat exchangers (ITT) and beaucoups cold
seawater to do the cooldown. Up to 80C, down to 25C for culture. Now
it's just a matter of plumbing (time & energy). Hope to vary the dwell
time, do plating work on the water and see what gives.
Aquaculture, 134 (1995):257-268
Food consumption rates of gilthead seabream larvae from first
feeding to 20 days of age were studied by feeding larvae on two
types of microcapsule (hard- and soft-walled) having diameters
ranging from 25 to 400 micrometer. Experiments were carried out
in 15-litre beakers using larvae cultured with standard
techniques and fed on rotifers and Artemia sp. nauplii. Ingestion
rate ranged from 3 to 35 particles/larva/h but, except for some
increase during the first days of feeding, no consistent trend
was observed in relation to larval weight. However, when values
were converted to volume or dry weight units, food consumption
rate increased progressively with increasing larval weight. On
a volume basis, the rate of this increase was different for the
two microcapsule types, being generally higher with soft
microcapsules, probably due to its better accessibility and to
their easier progress through the digestive tract. However, on
a dry weight basis the rates of food consumption were similar
with both types of microcapsule because of the higher density of
hard-walled microcapsules. Ingestion rates increased from 0.5-3
microgram/larva/h at first feeding up to 18-25 microgram/larva
microgram/h in older larvae. The daily specific ration increased
from O.5 to 2.5 microgram food/microgram larva/d at first feeding
to a maximum of 3-5 microgram food/microgram larva/d at a larval
dry weight of 70-110 microgram. Above this larval weight, the
specific ration tended to remain constant. The results show that
gilthead seabream larvae can be transferred directly from live
to microencapsulated food without appreciable variation in the
incidence of feeding or in the rate of food consumption from
first feeding onwards.
Aquaculture, 134 (1995):269-278
The capacity of hatchery-reared gilthead seabream larvae to
disintegrate mixed-walled protein/carbohydrate microcapsules in
their midgut was studied. The response of feeding larvae to eight
types of microcapsules was examined. The effects of the following
factors, which could potentially influence capsule breakdown,
were evaluated: (a) larval age; (b) addition of enzymes to the
diet; (c) concentration of cross-linking agent; and (d) procedure
for isolating microcapsule after formation.
The results revealed that larvae belonging to the same population
exhibited substantial individual variability in their capacity
to disrupt the microcapsule wall. Despite this, there were clear
differences in the ability of the larvae to break down different
types of microcapsules, depending principally on the technique
followed during the isolation phase of microcapsule elaboration.
Thus, capsules isolated in gelatin (type G) were more easily
broken down than those isolated in alcohol (type A),irrespective
of larval age ( P<0.001 ) . Addition of enzymes to capsules did
not result in any significant changes (P>0.05) in the degree of
capsule breakdown. Likewise, the concentration of cross-linking
agents used to form the capsule walls had no effect on capsule
disruption by the larvae.
The present results suggest that seabream larvae are able to
digest inert food from the onset of exogenous feeding. Their
capacity to do so is, however, influenced by the thickness of the
capsule coating and by their age. The results of this study also
contribute to our knowledge of the behaviour of a cultured larval
population in the presence of microencapsulated food.
Aquaculture, 134 (1995):307-311
Preferences between microencapsulated particles and phytoplankton
cell food particles by P. japonicus larvae were studied. The gut
pigment content method was used when both types of particle, in
the same proportions, were offered suspended in the medium. A
lack of feeding selectivity between both types of particles was
found for zoea stages, whereas mysid feeding was based on a
preferential ingestion of microencapsulated particles. The
feeding mechanism and the effects of particle morphology are
discussed.
Aquaculture, 134 (1995):325-337
Ascorbic acid (AA) is an essential nutrient both in particle and
live aquafeeds. In order to better assess the needs for this
nutrient during larviculture the AA content of algae, rotifers
and Artemia was studied with respect to their suitability at
startfeeding. In general, the microalgae evaluated were rich in
AA (1000-4000 microgram AA/g DW), but showed a considerable
variability among the different species: e.g. the concentration
in Isochrysis and Chlorella reached values 3-to 4-fold the
percentage of Tetraselmis (0.11% of DW). Brachionus routinely
cultured on Chlorella contained 2300 microgram AA/g DW. Cysts of various
batches and strains of Artemia differed considerably in ascorbic
acid-2-sulphate (AAS) concentration (296-517 microgram AA/g
DW).The amount of AA available in the freshly-hatched nauplii
reflected exactly the AAS reserve present in the cysts, what
evidences the complete conversion of AAS to free AA during
completion of embryonic development into nauplii.
Boosting techniques both for Brachionus and Artemia using
ascorbyl palmitate (AP) as the vitamin C source were established.
The addition of 20% AP in the diet of Brachionus enhanced their
AA content 10-fold over 3 days of culture. Supplementation of the
enrichment emulsion for Artemia with 20% AP increased the AA
content up to 2000 microgram/g DW after 24 h enrichment. This
lipophilic derivative of AA appeared to be a stable form of
vitamin C for enhancing AA levels in the live diets during
culture and/or enrichment. This bioencapsulation method provides
a tool for hatcheries to build up high AA concentrations in the
live prey administered to first feeding larvae of aquaculture
organisms in case of specific requirements (e.g. with respect to
handling stress, deformities).
A survey of commercial hatcheries indicated that a wide range of
products is used for the cultivation and boosting of rotifers,
which consequently affect their AA levels. In general, the AA
content in the algae and, consequently, the algal enrichment of
Brachionus tended to score lower in the hatcheries than under lab
conditions.
Aquaculture, 134 (1995):351-359
Tricaine, quinaldine sulfate, and metomidate were compared as
anesthetics for larvae of two species of fish, red drum
(Sciaenops ocellatus) and goldfish (Carassius auratus). Larvae
were exposed to various concentrations of each anesthetic and the
percentages of fish reaching stage 4 of anesthesia, post-exposure
recovery, and survival were recorded. Effective concentrations
were defined as those which induced stage 4 of anesthesia within
3 min after exposure with a recovery time of 10 min or less.
Post-exposure survival of 100% was an additional criteria used
to define effective anesthetic concentrations. The lowest
effective concentration of tricaine for red drum was 55 mg/l
(26=F8C), while 50 mg/l (24=F8C) was the lowest effective
concentration for goldfish. The lowest effective concentration
of quinaldine sulfate for red drum was 35 mg/l (26=F8C), while 60
mg/l (24=F8C) was the lowest effective concentration for goldfish.
Metomidate was found to be an ineffective anesthetic for both red
drum and goldfish larvae based upon survival and recovery times.
Mortality occurred in red drum larvae at all tested
concentrations of metomidate. Larvae of both species that
survived anesthesia with metomidate had longer induction and
recovery times compared to larvae exposed to tricaine and
quinaldine sulfate.
(the author is lecturer at the Faculty of Fishery of Can Tho
University in Vietnam, and has been working in shrimp farming for
over seven years, at hatcheries, nurseries and farms. He has also
worked with Artemia at small-scale salt farms in the Mekong
Delta. His research covers shrimp farming systems, the technical
and socio-economic aspects of shrimp farming, and the
environmental impact of shrimp farming on mangroves in the Mekong
Delta For more information on this subject, contact Cao Thang Binh,
Aquaculture Program, AIT. G.P.O. 2754, Bangkok 10501,
Thailand (phone 66-2-524-5485,fax 66-2-524-6200, email 949658@
recvax.ait.ac.th).
Artemia culture in Vietnam was initiated in 1983 when researchers
at Can Tho University imported cysts and began experiments in
Vinh Chau District, where farmers produced salt during the dry
season and shrimp during the wet season. Artemia production was
integrated into this cycle and became profitable in 1988.
Artemia are cultured in salt evaporation ponds during the dry
season. Every day, high salinity water is removed from the
Artemia ponds and channeled to nearby salt extraction ponds. It
is replaced with water from a low-salinity reservoir. During the
rainy season, when salinity levels are too low for Artemia
production, the ponds are used for shrimp culture.
Either dried or wet Artemia cysts can be used to inoculate the
ponds. Wet cysts are dehydrated by immersion in salt-saturated
water for a few hours before incubation. Incubation is carried
out in conical jars or buckets supplied with strong aeration.
Incubating density ranges from 3 to 5 grams of dried cysts per
liter and inoculating densities ranged from 200 to 300 grams of
dried cysts per 0.5-hectare pond (approximately 1 kg of dried
cyst equals 2.5 kg of wet cysts). The inoculation of nauplii was
usually carried out in the early morning or late evening when the
water temperature was low. Nauplii were gently released along all
four dikes.
In nearby reservoirs, we culture algae to feed the Artemia.
Chicken manure and rice bran are also used to feed adult Artemia.
Chicken manure is placed in bags or bamboo baskets and immersed
in water for 2 days. Then it's spread over the pond. Rice bran
is mixed with water in a bucket and fed directly to the Artemia.
Feed amount is based on the Artemia population, pond water color,
and the amount of algae pumped per day. On average. about 80-100
kilograms of chicken manure and 10-20 kilos of rice bran were fed
per hectare per day. Trials with pig and cattle manure resulted
in lower cyst production.
Annually, with this integrated system, farmers averaged 84
kilograms of Artemia cysts (wet weight), 371 tons of salt, and
164 kilograms of shrimp per hectare. More intensive systems
produced up to 150-200 kilograms of wet cysts per hectare. From
1990 to 1994, approximately 150 hectares in Vinh Chau District
(Soc Trang Province) and Vinh Hau District (Minh Hai Province)
produced 8-10 tons of wet cysts annually. If Artemia biomass is
used for nursing shrimp fry or for semi-intensive culture, more
profits and higher shrimp production can be expected. The results
indicate a great potential for developing this system, although,
at the present time, it's confined to a small area because
Artemia culture requires know-how and investment.
The integration of Artemia production with traditional methods
of salt/shrimp production offers many advantages. Artemia biomass
is used to feed the shrimp. The high densities of phytoplankton
in the waste water of the shrimp ponds is pumped to the Artemia
ponds, where the Artemia consume the algae and, in the process,
clean the water. Then, the high saline "algae-free" water from
Artemia ponds is channeled to salt extraction ponds.
Although Artemia cysts could be exported at high prices, the
farm-gate price is still quite low. In 1989, it was only 0.5 U.S.
dollar for a kilogram of wet cysts. After that it increased to
3-4 U.S. dollar in 1990, 5 U.S. dollar in 1991, and 10 U.S.
dollar in early 1995. Obviously, the expansion of Artemia culture
in the Mekong Delta heavily depends on the market for Artemia
cysts, farmers'investment ability, and the extension of Artemia
culture techniques.
Wild Postlarvae: In pond systems affected by TS, the survival of
captured wild postlarval Penaeus vannamei has been apparently
higher than that found for postlarvae which have come out of
hatcheries. Thus, if available, wild postlarvae may be the most
appropiate to stock on farms with a history of losses from TS.
Alternate Species: Transmission (infectivity) trials reported in
this paper which compared the relative sensitivity of juvenile,
SPF P.vannamei and P. stylirostris indicated that P. stylirostris
was far less sensitive to TSV than P. vannamei. This provides a
clue that P.stylirostris may serve as an effective, alternate
shrimp species which can be farmed instead of P.vannamei in areas
affected by TS. However, P.stylirostris will probably not be
effective in those shrimp farming areas where IHHNV
is endemic, unless a specific pathogen resistant (SPR) strain of
P.stylirostris is available.
TSV Resistant P.vannamei: Taura Syndrome results in a marked
mortality of exposed populations of farmed P.vannamei. We have
observed in raceway populations in Hawaii that within a few weeks
of a TS epidemic the survivors display no outward indications of
TS. These shrimp go on to grow and perform normally. The
mechanism for this apparent 'resistance' is unknown. However,
perhaps, these shrimp have a tendency that is inheritable. If
this is the case, then, potentially, these animals have been
rigorously selected for and could serve as a founder stock for
a program to selectively breed for resistance to TSV. Another
possibility is that the survivors received a sublethal exposure
to TSV and were able to develop an induced (immune mediated)
resistance to the agent.
Hatchery managers used to be skeptical about stylirostris, but
now (September 1994) they realize it is easier to work with than
vannamei. Hatcheries are now producing equal amounts of vannamei
and stylirostris. Some hatcheries produce 100% stylirostris.
Ecuador: Jerome Thompson owner of Intensive Culture Systems,a
consulting firm which specializes in closed system shrimp
farming, reports:
When I arrived [1994] in Guayaquil, Ecuador, I noticed that most
of the mortality from Taura seemed to occur during the first week
that the animals were exposed to pond/river water (PL-12 to
PL-20). By the end of the second week most of the mortality
seemed to have subsided. I put together a small closed system
consisting of 2 holding tanks and an interconnected biofilter
tank. The idea was to protect the PLs during what I believed to
be the period of maximum susceptibility. The first experiment
consisted of stocking the holding tanks and dividing the
population into three groups (each with three replicates). The
first group, the control, was held for three days in the system
(typical acclimation time at this farm) and then stocked in
growout ponds. The second group was held in the system for 15
days and then stocked, while the third group was held in the
system for 30 days and then stocked. Each group was grown for 120
days. At harvest, the control group was 123-days-old, the second
group was 135-days-old, and the last group was 150-days-old.
Survival in the control group was about 25%, in the second group
about 48%, and in the third group about 58%. Average survival at
this time for animals acclimated without closed system was
between 12% and 15%. Not only did the control group have the
poorest survival, but it also had the smallest shrimp. The
animals in the control group weighed about 11 grams at harvest,
while the 30 day animals were between 15 and 16 grams.
(excerpts from article "Taura, Taura, Taura" in Shrimp News
International, Sept./Oct. 1995)
Since 1991, fourteen hatcheries have received permits to operate
on the Gulf of Fonseca. Nine are currently in operation. They
could supply 32% of the country's seed requirement. In addition,
each year, GMSB, Inc,. a Honduran owned hatchery in Florida,
supplies an additional 34% of the country's requirement, or 1.2
billion Penaeus vannamei postlarvae, to its parent company in
Choluteca, Honduras. The remaining 36% of the seedstock is
supplied by fishermen and other imports.
Of the nine hatcheries in operation, four produce less than 10
million postlarvae per month; the remaining five produce between
20 and 25 million per month. Currently, there are no combination
hatchery/maturation systems in Honduras.
Close communications between Grupo Granjas Marinas, S.A., in
Honduras, and GMSB, Inc., the hatchery in Florida, allow us to
coordinate stocking schedules and hatchery production. These
communications address questions about the age and size of
postlarvae and help relieve the tension that surrounds postlarvae
transactions. The farms want the largest postlarvae possible and
the hatchery wants to ship the smallest animal possible. Several
tools allow us to attach a value to the quality of a group of
postlarvae, thus eliminating as much as possible, any subjective
grading by hatchery technicians and farm personnel.
One of the first criteria used in the hatchery is gill
development. Gills must demonstrate secondary branching before
a group of animals is considered ready to acclimation prior to
shipping. After acclimation a group of postlarvae to salinity
conditions on the farm, a sample of these animals is challenged
with a stress test at the hatchery. The stress test consists of
a mixture of salinity, temperature and pH adjustments and closely
matches the stress test given on the farm prior to introducing
the animals into the ponds. The results from these two tests
should compare favorably and depending on the percent of animals
that survive a grade for the group of postlarvae is calculated.
Depending upon the grade, the postlarvae can either be stocked
directly into a production pond or put through the nursery system
if quality appears marginal.
For the stress test, postlarvae are maintained in a tank with the
following environmental characteristics for four hours. Water 10
degrees lower than ambient, salinity 15 parts per thousand lower
than ambient and pH 0.5 lower than ambient. The percentage of
live and active animals after four hours is the grade for the
group. Healthy animals larger than an eight day old postlarvae
survive the challenge quite well. If there were no unanticipated
stresses during shipment, the hatchery test and the farm test
will give similar results. If there are significant differences
between hatchery and farm results, it is relatively easy to trace
them.
Our hatchery ships to five different farms, each having specific
salinity requirements that vary through the year. The task of
acclimating postlarvae several days prior to shipping is a real
challenge. Proper acclimation, however, is very beneficial
because it means stocking a stronger animal. Hatcheries, for the
most part, have more controls and equipment for safely
acclimating postlarvae than farms, where transfers may have to
be done on a pond bank, at night, and in the rain.
(from article by Bob Rosenberry in Shrimp News International, July 24, 1995)
a) Growth hormone and acceleration of fish growth rate
A major contribution to the growing worldwide demand for seafood will
undoubtedly come from aquaculture of finfish and shellfish. One possible
method to increase the efficiency of fish production is the application of
growth stimulating hormones. Although several hormones have the
disadvantages of acting on the human consumer, and like
steroids, are slowly biodegraded, growth hormones are not. Cross-activity
between different species is relatively rare. In the gilthead seabream
Sparus aurata it was shown that growth hormones from vertebrate sources have
low or no effect on growth rate. In addition, growth hormone (GH) is a
protein which undergoes quick denaturation by heat and
the physiological conditions in the mammalian digestive tract. Therefore, it
can be expected that the use of this protein in edible fish will have no
effect on the consumer.
GH can be produced in large quantities only by recombinant DNA technology. To
circumvent all problems which arise from introducing a foreign gene into
edible fish, it is proposed to produce the GH in bacteria and then purify it
by standard biochemical techniques. The pure protein will then be introduced
into the fish.
Several experiments were carried out on the growth rate of Sparus aurata,
using recombinant growth hormones from human, bovine, porcine and
chicken. The GH was injected intramuscularly or intraperitoneally twice each
month. Only a slight increase of about 15% in fish growth was obtained
when human or bovine GHs were administered.
The phylogenetic tree of GH consists of several trunks, and the four GHs
examined are on one trunk which is different from the teleost trunk.
Additional experiments ware therefore performed with recombinant fish GHs.
In one experiment, implants of salmon GH were prepared, and were
introduced subcutaneously. The implants were programmed to release the
hormone in about 100 days. No acceleration of growth resulted from such
treatment.
The salmon GH is on the teleost trunk of the phylogenetic tree; it is,
however, not on the same branch as the S. aurata. Another experiment was
performed with tuna GH, which is very closely related to the S. aurata .
Weekly injection of this hormone to S. aurata fish accelerated the growth
rate of the fish by about 50%.
It is now planned to produce the S. aurata GH, to inject it into fish, and
also to prepare implants with this hormone to be introduced
subcutaneously. It is believed that the growth acceleration will be at least
as good as that obtained with the tuna GH. The S. aurata GH cDNA was
cloned by us, and an expression construct was made. It was shown
that this construct produces the GH of S. aurata in large quantities.
In order to be able to market fish which were treated with the GH, it is
required to show that when the fish are marketed, the GH level in their
blood is similar to that in nontreated fish. For this reason, a native GH was
isolated and HPLC purified from pituitaries of fast growing S. aurata.
Antibodies were prepared to this GH, and served in Western blots to
detect S. aurata GH. It is planned to increase the
sensitivity of the detection by preparing a radioimmunoassay for S.
aurata GH.
b) The role of growth factors in early embryonal development
Experimental evidence suggests that the action of GH in mammals, and probably
in fish as well, is not direct, but is mediated by a group of growth
factors: somatomedins or insulin-like growth factors (IGF), especially IGF-I.
Very little is known regarding control of growth and differentiation in
fish during early stages of development. In order to study the expression
of this gene during early development, a cDNA coding for S. aurata IGF-I was
cloned.
Poly (A ')RNA, which was prepared from livers of adult S. aurata fish during
their fast growing period, was used for cDNA synthesis. Sparus IGF-I was
then cloned using PCR techniques. Sequences for the 5' untranslated region, the
signal peptide and part of the beta domain sequence were determined from the
genomic clone. Based on these data, the remaining coding sequence was
obtained by anchored PCR and 3' RACE. The composite sequence of Sparus
IGF-I cDNA contains a 546 nucleotides open reading frame and encodes 182 amino
acids of the pre-proIGF-I.
Based on the sequence of this cDNA, two primers were designed in order to use
the highly sensitive reverse transcription-polymerase chain reaction
(RT-PCR). It was found that a fragment of 237 nt was amplified from total
RNA prepared from unfertilized eggs, and also in embryos at 4, 8, and 12 hours
after fertilization as well as in larvae on the day of hatching. It was
verified that the amplified fragment was IGF-I. These results suggest that
maternal IGF-I transcript is present in fish eggs.
The presence of IGF-I gene in fish embryos may indicate that growth factors
are important during early development. Presence or function of other
growth factors has not been studied in fish. In addition to the importance of
studying the function of growth factors in embryonic development of fish,
fish may serve as a model system for studying the molecular biology of
vertebrate development. A small aquarium fish, the Japanese medaka, was chosen
for this study. The advantages of this fish system are as follows: they
can be easily maintained in the laboratory, and large numbers
can be bred on a routine basis; eggs and embryos can be made available all
year round; fertilization and development are external; the eggs and
embryos are translucent, and embryogenesis can be observed easily under a
stereomicroscope; the medaka has a short life cycle of 3 to 4 months.
To examine whether sequences that are homologous to the growth factor cDNAs
from different organisms are present in the genome of medaka, a probe
specific for each growth factor was used. A number of hybridization bands were
detected with each of the growth factor probes tested. These data strongly
suggested that in medaka these growth factors are present.
A cDNA library was prepared from the whole body of medaka, and the cDNAs of
basic fibroblast growth factor (bFGF), transforming growth factor-alfa
(TGF-alfa) and transforming growth factor-beta (TGF-beta) are now cloned.
In addition, the effect of these growth factors on developing medaka embryos
was studied. For assessing the rate of embryo development, the incorporation
of radioactive labelled thymidine into the DNA fraction of the embryo was
determined. It was found that addition of bFGF to the rearing medium caused an
acceleration of 3H-thymidine incorporation into the embryos. It is known
that embryos that grow faster are of better quality than slow growing
embryos.
c) Somatolactin, a newly discovered pituitary hormone
Somatolactin (SL) is a glycoprotein newly isolated from pituitaries of
teleosts. It is related to the growth hormone/prolactin family, produced
by the pars intermedia cells, and secreted to the blood. The physiological role
of the somatolactin is currently unknown. However, the conserved nature of SL
indicates that it may have a very important function.
It is planned to elucidate the physiological role of this hormone in S. aurata
SL was isolated from the pituitary by alkaline extraction, gel filtration
on a Sephadex G-100 column, and reversed-phase high-performance liquid
chromatography (rpHPLC) on a TSK gel ODS-120T column. The purified protein was
confirmed to be somatolactin by immunoblotting using chum salmon somatolact in
antisera. It was found that S. aurata SL consists of at least two forms.
One form (28 kDa) is probably a glycosylated form, while the other (25 kDa) is
a simple protein form, as was also found in Atlantic cod.
For determination of the primary structure, the SL was digested with lysyl
endopeptidase and with endoproteinase Asp-N, and cleaved with cyanogen
bromide. The resulting fragments were separated by rpHPLC and subjected to
sequence analysis on an automated gas-phase sequencer employing an Edman method.
It was found that the S. aurata SL consists of 207 amino acids. Alignment of
its sequence with the SL sequences of flounder, halibut, lumpfish, chum
salmon and Atlantic cod, showed remarkable conservation of the SL sequence of
86%, 83.5%, 78%, 76% and 71.5%, respectively.
In order to clone the cDNA of SL, the cDNA library of S. aurata was screened
with cod and flounder SL cDNA probes. A fragment of about 2.5kb was
isolated from several recombinant phages, and it is now being analyzed for
the nucleotide sequence. With the amino acid and nucleotide sequences in hand,
it will be possible to study the function of SL in this fish.
(article in Israel Oceanographic & Limnological Research, Biennial Report
1992 -1993)
The increased world wide demand for edible marine shrimp resulted in the
development of large scale aquaculture of penaeid shrimp in South America
(mainly Penaeus vannamei) and Southeast Asia (Penaeus monodon and P.
japonicus). The species P. semisulcatus was found to be the most appropriate
one for culture in the southern part of Israel.
Following the success in producing large quantities of post larvae with high
survival rates, there remain two main problems which must be overcome in
order to reach the stage of commercia1 production of the shrimp. The first one
is the development of an adequate, cheap pellet food diet that will promote
fast growth of post larvae to commercia1 size. Secondly, full control
over the reproductive cycle is required to permit year-round production of
good quality eggs. This necessitates research into the processes
associated with oocyte development (vitellogenesis) and their hormonal
control.
Lipids constitute up to 30% of the wet weight of ovaries. Phospholipids and
triacylglycerols containing saturated and unsaturated fatty acids were
found to accumulate in the ovaries of P. semisulcatus during vitellogenesis.
These lipids originate in the food and accumulate in hepatopancreas on
route to the ovary. Triacylglycerols and phospholipids were found in the
high density lipoprotein (HDL) fraction that was prepared by density gradient
ultracentrifugation from the hemolymph of vitellogenic females. The
triacylglycerols were not detected, however, in either the HDL of males
or that of non-vitellogenic males. Two lipoproteins were identified in the HDL
of vitellogenic females: vitellogenin (the female specific protein) and
LP1. The LP1, which was also found in male HDL showed one ~ 100kDa
polypeptide in SDS gel electrophoresis, under reducing conditions. The mode
transport of lipids by the lipoproteins from the food consumed in gut
and/or the lipids stored in the hepatopancreas is the main objective live of a
current research project. The results are relevant for formulation of
diets required to promote growth and reproduction.
Evidence accumulating in our laboratory points to intra-ovarian synthesis of
vitellin, one of the most prominent proteins in developing oocytes.
Immunoisolation from cell-free translation of poly(A+)RNA using antiserum
against purified vitellin produced a 35 kDa polypeptide. It is assumed
that the difference between this polypeptide and the larger 2-4 subunits
(MW ranging from 80-158 kDa) found in the native Vt (MW =3D 283 kDa) is due to the
non-glycosylated nature and lack of bound phosphate in cell-free translation.
Indeed, the removal of oligosaccharides from purified Vt by enzymatic
digestion with N-glycosidase F resulted in a smaller polypeptide of 36 kDa,
which is very close to the molecular weight of the translation product.
Synthesis of cDNA to poly(A+) RNA that was extracted from vitellogenic ovaries
resulted in a major band which was detected by ethidium bromide staining.
This band, as well as a cDNA insert purified from the library, was estimated
to have 1.1 kb. Both hybridize to mRNA prepared from ovaries or hepatopancreas
of vitellogenic females, but did not hybridize to mRNA prepared from the
hepatopancreas of males and non-vitellogenic females, testes
or subepidermal adipose tissues. These results suggest that vitellin, which
is produced in the ovary, and vitellogenin, which is synthesized in the
hepatopancreas, are the gene products of one gene. We plan to study the
regulatory mechanisms which determine the level of expression of vitellin
and vitellogenin during the process of vitellogenesis.
(article in Israel Oceanographic & Limnological Research, Biennial Report
1992-1993)
BASICS FOR RAISING BRINE SHRIMP
Kai Schumann is an engineer in a biotech company, and has made a FAQ for
Artemia culture, with information he has gathered from various books,
publications and his own experience. It contains very practical and
useful guidelines for hatching and culturing Artemia. The text can be
obtained from Kai Schumann, 4901 Mt. Gaywas Dr., San Diego, CA 92117,
USA, email SCHUMANN_KAI@Lilly.com. He would appreciate very much
receiving more information on the subject, as well as comments or
additions to this FAQ.
BIVALVE LARVAE METAMORPHOSIS 1
By Tom Lewis
Department of Agricultural Science
University of Tasmania
GPO Box 252C
HOBART
Tasmania, Australia, 7001
Phone: (002) 20 2776
Fax: (002) 20 2642
BIVALVE LARVAE METAMORPHOSIS 2
By Will Borgeson
BIVALVE LARVAE METAMORPHOSIS 3
By Tom Lewis
Garland et al (1986) Aust J Mar Freshwater Res 37 pp 713-720
COD FARMING
By Rodney Melvin Penney
I am also interested in the development of new species for
aquaculture and would like to get involved in cod aquaculture in the
future. I would like to discuss this further in the future. I hope
this information was helpful to you.
CONCLUDING REMARKS OF THE LARVI'95 LARVICULTURE CONFERENCE HELD IN GENT,
BELGIUM, SEPTEMBER 3-7, 1995
Impressions of the meeting presented at the closing ceremony on behalf of
the academic community by Dr B R Howell (Fisheries Laboratory, Ministry
of Agriculture, Fisheries & Food, Conwy, UK)
While this part of the nutrition story gradually unfolds, other
aspects of nutrition are perhaps being neglected. For example, the role of
lipids vis-a-vis free amino acids and monosaccharides was barely
mentioned, though there were some valuable contributions on the importance of
vitamin C for both broodstock fish and larval fish and crustacea.
T. Lam
Larvi'95 - Concluding Remarks - Private Sector Participants
prepared by Richard Prickett (Marine Farm Technology, Ltd., UK)
and Gidon Minkoff (Israel Salt Co Ltd., Israel)
Also we fish farmers tend to pick up odd ideas from lectures which are often
not part of the main presentation. One example of this was the use of water
jets instead of air for surface cleaners in larval tanks given in a paper on
flatfish farming in Ecuador. I remember looking at the audience and seeing
everyone who was working in a marine fish hatchery making a note in their
books!
Finally we have already received some feed-back on future research and
development projects from colleagues in the private sector. These cover such
areas as:
We hope these views are seen as being constructive and will lead to further
discussions in the future on a mutually beneficial basis.
HATCHERY HYGIENE MANUAL
By Tom Lewis
INDIAN SHRIMP FARMING HIT BY DISEASE
An outbreak of the so-called white patch disease has taken a
heavy toll on shrimp farming, resulting in a loss of about Rs180
million ($5.7m) in coastal India's Andhra Pradesh last year,
according to the Press Trust of India.
LABORATORY STUDIES ON THE CULTURE OF THE BRINE SHRIMP ARTEMIA USING
ORGANIC WASTES
Short Communication by J.A. Basil, V.K.S. Nain and A.J. Thatheyus
School of Biological Sciences, Madurai Kamaraj University, Madurai 62501,
India.
COLLECTION OF WILD SHRIMP SEED IN INDIA
In India, the shrimp farming boom has prompted school children
to collect wild shrimp seed from small saline embankments. They
collect the seed and sell them to seed collectors (middlepersons)
at 0.6-1.5 Rupees/piece for Penaeus monodon and 0.2-0.5
Rupees/piece for P. indicus (US$1=3D Rp31.75). Simple hand-made
scoop nets of different sizes are used. A middleperson prepares
lots of about 5,000-10,000 seed and supplies them to the growout
ponds (improved extensive and extensive systems). The children
collect 30-40 P. monodon and P. indicus seed per day, and earn
about US$1 for about one hour's work at both dawn and dusk. The
cost of P. monodon seed is three times more than the P. indicus
seed. The size of the collected postlarvae varies and may reach
7 g.
TECHNICAL APPRAISAL MANUAL - SHRIMP AND FRESHWATER PRAWN HATCHERY-
1994
S.K. Gosh, K. Planisamy and S.C. Pathak (Eds), published by the
National Bank for Agriculture and Rural Development (NABARD),
India, 87 pp.
Overseas price: US$ 10. For information, contact the General Manager,
GAPD, NABARD, PB No. 6552, Worli, Bombay 400018, India.
LARVAE AND BACTERIA
By Scott Feindel
Nantucket Shellfish Hatchery
Nantucket, MA
LARVAE METAMORPHOSIS 1
By Tom Lewis
LARVAE METAMORPHOSIS 2
By Will Borgeson
Perhaps the reason I have had good luck with pasteurization is
that I deliver the seawater to the (previously bleached and debleached)
algae culture vats when the water is still at 75 degrees C. Submicron
filtered air is bubbled into the vats overnight to help cool the water
and to maintain positive pressure in the (covered) vats so that pathogens
cannot enter. Typically an inoculum and nutrients are added the next
morning. Within a few days the *Isochrysis* cultures are in the range of
1.5 million to 2 million cells/ml, and are ready to feed to larvae.
WATER TREATMENT IN ALGAE CULTURE 1
By Will Borgeson
WATER TREATMENT IN ALGAE CULTURE 2
By Robert Rheault
Moonstone Oysters
WATER TREATMENT IN ALGAE CULTURE 3
By Will Borgeson
LARVAE AND BACTERIA
M. Yufera, C. Fernandez-Diaz, E. Pascual
Instituto de Ciencias Marinas de Andalucia (C.S.I.C.), Apartado
Oficial, 11510 Puerto Real, Cadiz, Spain
Abstract:
CAPACITY OF GILTHEAD SEABREAM, SPARUS AURATA L., LARVAE TO BREAK DOWN DIETARY
MICROCAPSULES
C. Fernandez-Diaz, M. Yufera
Instituto de Ciencias Marinas de Andalucia (C.S.I.C.), Apartado
Oficial, 11510 Puerto Real, Cadiz, Spain
Abstract:
FLUOROMETRIC DETERMINATION OF SELECTIVITY BETWEEN LIVE AND INERT FOOD
BY PENAEUS JAPONICUS LARVAE
V. Marin-Magan, J.P. Canavate
CICEM 'El Toruno' Junta de Andalucia, P.O. Box 16, 11500, Puerto
de Santa Maria, Cadiz, Spain
Abstract:
VARIATION OF ASCORBIC ACID CONTENT IN DIFFERENT LIVE FOOD ORGANISMS
G. Merchie, P. Lavens, Ph. Dhert, M. Dehasque, H. Nelis,
A. De Leenheer, P. Sorgeloos
Laboratory of Aquaculture & Artemia Reference Center, Rozier 44,
B-9000 Gent, Belgium
Abstract:
THE EFFECTIVENESS OF TRICAINE, QUINALDINE SULFATE AND METOMIDATE AS
ANESTHETICS FOR LARVAL FISH
K.C. Massee, M.B. Rust, R.W. Hardy, R.R. Stickney
School of Fisheries, WH-IO, University of Washington Seattle WA
98195,USA
Abstract:
ARTEMIA CULTURE IN THE MEKONG DELTA OF VIETNAM
(correspondence from Cao Thang Binh to Shrimp News International,
Sept./Oct. '95)
TAURA DISEASE
In mid-June 1995, survivals of wild-caught seed were ranging from
50% to 60%; survivals of hatchery-produced seed, 20% to 30%. Some
evidence suggest that good old vannamei has already become more
resistant to the virus, in the same way that stylirostris appears
to have become more resistant to the IHHN virus in Mexico's Gulf
of California.
HATCHERY DEVELOPMENTS IN HONDURAS
At the Symposium, Jim Norris, manager of GMSB's big hatchery in
Florida, talked about hatchery developments in Honduras. He said,
in April 1995, there were approximately 11,050 hectares of shrimp
ponds in Honduras, requiring approximately 3.5 billion postlarvae
a year. Here are some excerpts from his presentation:
MOLECULAR BIOLOGY AND GENETIC ENGINEERING OF FISH
by Benzion Cavari and Bruria Funkenstein
CRUSTACEAN REPRODUCTION STRUCTURE AND BIOSYNTHESIS OF
LIPOPROTEINS AND ACCUMULATION OF LIPIDS IN THE OVARY
by Bruria Funkenstein and Esther Lubzens