Laboratory of Aquaculture & Artemia Reference Center

“Aquatic Animal Disease Diagnostics", the fifth in the AquaTT-led, Marie Curie funded series known as AQUALABS. The course will take place between 15 - 20th January 2006 inclusive at University of Stirling, Scotland. The application deadline is 2nd December 2005 and complete applications (CV, application form, motivation letter, recommendation letter and Proof of Identity) must be sent via e-mail to lorraine@aquatt.ie

“Design and Operation of Recirculation Technologies", the sixth in the AquaTT-led, Marie Curie funded series known as AQUALABS. The course will take place 27th February 2006 – 3rd March 2006 inclusive at Wageningen University, the Netherlands.The application deadline is 13th January 2006 and complete applications (CV, application form, motivation letter, recommendation letter and Proof of Identity) must be sent via e-mail to lorraine@aquatt.ie

If you require any further information please visit the AquaTT website, www.aquatt.ie

Ms. Lorraine Rafferty
Project Officer, AquaTT
PO Box 8989, Dublin 2, Ireland
T +353 1 644 9008, F +353 1 644 9009
lorraine@aquatt.ie
www.aquatt.ie

Special EAS Publication N° 35
"LESSONS FROM THE PAST TO OPTIMISE THE FUTURE"
which resulted from the Aquaculture Europe 2005 conference, Trondheim, Norway, August 5-9, 2005.
For more details and for ordering we refer to our web site http://www.easonline.org/publications/en/catSP35.asp.

Sofie Vanroose
Registrations Co-ordinator – EAS Membership Services – Publication Sales
European Aquaculture Society
Slijkensesteenweg 4
BE-8400 Oostende – Belgium
Tel: +32 59 323859 Fax: +32 59 321005
www.easonline.be

EFFECT OF TEMPERATURE AND FOOD AVAILABILITY ON REPRODUCTIVE INVESTMENT OF FIRST-TIME SPAWNING MALE ATLANTIC COD, GADUS MORHUA
Michio Yoneda, Peter J. Wright-2005
ICES Journal of Marine Science 62 (7): 1387-1393
Abstract:

This study demonstrates how temperature and food availability affect growth, maturation, and sperm production in first-time spawning male cod in captivity. Cod, prior to the onset of maturation, were held under four different varying temperature and feeding regimes between November 2002 and March 2003. Lower food availability resulted in poor growth and body condition. Decreasing temperature partly led to slower growth in fish that matured during the experiment. Low temperature resulted in lesser proportions of mature fish relative to the higher temperature treatments. Higher temperature and food availability resulted in higher sperm production (testicular weight and gonadosomatic index). Our findings suggest that variation in food availability would mainly affect the growth and condition and the level of gamete production whilst variation in temperature would affect the proportion of males that mature. These results are contrasted with similar data for female cod.

(Tohoku National Fisheries Research Institute, Shinhama, Shiogama 985-0001, Japan; email of M. Yoneda: myoneda@fra.affrc.go.jp)

ESTIMATION OF GROWTH AND FOOD CONSUMPTION IN JUVENILE JAPANESE FLOUNDER PARALICHTHYS OLIVACEUS USING CARBON STABLE ISOTOPE RATIO d13C UNDER LABORATORY CONDITIONS
Yoshihiro Watanabe, Tadahisa Seikai, Osamu Tominaga-2005
Journal of Experimental Marine Biology and Ecology 326(2): 187-198
Abstract:

To estimate the accumulated food consumption and growth of juvenile Japanese flounder Paralichthys olivaceus, we investigated the relationships between individual food consumption and growth, and the change in the stable carbon isotope ratio (d13C). Japanese flounder juveniles were individually reared and their diet was switched from one formulated feed EP1 (d13C = - 19.47‰) to another EP3 (d13C = - 17.21‰) and fed at different feeding regimes. After the switch, the d13C content of the dorsal muscle was exponentially shifted to a different level in proportion to the feeding and growth rates. Therefore, measuring the carbon stable isotope ratio is a useful tool for estimating the food consumption and growth rate of juveniles. In addition, since the velocity of change and the asymptotic value of the carbon stable isotope ratio varied in muscle, caudal fin and liver tissue, different tissues can be used for different time scale estimations.

(Faculty of Biotechnology, Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, Fukui, 917-0003, Japan; email of O. Tominaga: tominaga@fpu.ac.jp)

EFFECT OF VARYING DIETARY LEVELS OF O6 POLYUNSATURATED FATTY ACIDS DURING THE EARLY ONTOGENY OF THE SEA SCALLOP, PLACOPECTEN MAGELLANICUS
Fabrice Pernet, V. Monica Bricelj, Christopher C. Parrish-2005
Journal of Experimental Marine Biology and Ecology 327(2): 115-133
Abstract:

This study investigated the effects of selected microalgal diets on growth, survival and fatty acid composition of sea scallops, Placopecten magellanicus, from egg hatching to postlarvae. Scallops were offered Pavlova lutheri (MONO) and Pavlova sp. (strain CCMP 459, P459) in combination with Chaetoceros muelleri (CHGRA) and P459 alone. These diets exhibited varying proportions of ?6 docosapentaenoic acid (22:5?6, DPA) which represented 8.9% of total fatty acids in P459 compared to 5.4% in P459–CHGRA and only 0.5% in MONO–CHGRA. For experiment I, larvae were fed three diets (MONO–CHGRA, P459–CHGRA or P459 alone) for 35 days after fertilization. For experiment II, larvae were fed P459–CHGRA for 21 days and split among the three diets until 39 days post-fertilization. For experiment III, 4-day-old larvae were exposed to P459–CHGRA until they become postlarvae. MONO–CHGRA failed to produce pediveligers when fed to early veligers but yielded competent larvae when fed to late veligers. This may be related to the low ?6 DPA content of this diet. High accumulation of DPA by early veligers suggests a nutritional requirement for this fatty acid. Unialgal P459 supported lower pediveliger production and lower growth rate than other diets containing CHGRA. This may be the effect of higher levels of energetic substrates in CHGRA-containing diets. Finally, P459–CHGRA yielded the best survival and growth rate during the whole larval period. All three experiments showed marked arachidonic acid (20:4?6, AA) accumulation in early veligers (4 to 21 days) and in pediveligers (32 to 43 days). Accumulation of AA during metamorphosis might reflect stimulation of immune functions due to pathogen infection and degradation of larval organs or the role of AA in cell signalling processes associated with tissue reorganization. Early veligers markedly accumulate DPA likely in response to low docosahexaenoic acid (22:6?3, DHA) concentrations in the three tested diets. The potential role and effect of DPA as a substitute for DHA is discussed.

(Institute for Marine Biosciences, National Research Council, 1411 Oxford Street, Halifax, Nova Scotia, Canada B3H 3Z1; email of F. Pernet: fpernet@umcs.ca)

OVARY DEVELOPMENT AT THE ONSET OF GAMETOGENESIS IS GENETICALLY DETERMINED AND CORRELATED WITH REPRODUCTIVE TRAITS AT MATURITY IN SHRIMP LITOPENAEUS (PENAEUS) VANNAMEI
Fabiola G. Arcos, Ilie S. Racotta, Elena Palacios, Ana M. Ibarra-2005
Marine Biology 148 (2): 339 - 346
Abstract:

Besides some mammals and a few model organisms, the presence of genetic variation in ovary or gonad development at ages before that of reproduction has not been established for marine oviparous species nor has the correlation with reproductive traits at maturity. In this investigation, ovary development was evaluated for genetic variability in a full-sib family structured population of subadult shrimp. The numbers of each oocyte type that were present were counted, measured, and used to evaluate the following traits: total oocyte number, mean oocytes diameter, and ovary maturity (OM). The total ovary area was also measured for each female. Genetic variation was assessed through the estimation of the parameter ‘heritability’. The heritability (h 2) of total number of oocytes was zero, but large heritability values were seen for mean oocytes diameter (h 2=0.57±0.27) and OM (h 2=0.71±0.26). Family means correlations between traits in subadults with traits measured in their full-sibs when adults (days to first spawn, total number of spawns, total fecundity, and fecundity at first spawn) indicated the existence of some significant associations between reproductive traits at the two ages. These findings point toward an early genetic determination of reproductive capacity in this crustacean.

(Centro de Investigaciones Biológicas del Noroeste S.C., A.P. 128, La Paz B.C.S., 23090 Mexico, Mexico; email of A. Ibarra: aibarra@cibnor.mx)

GENETIC VARIATION IN WILD AND HATCHERY STOCKS OF SUMINOE OYSTER (CRASSOSTREA ARIAKENSIS) ASSESSED BY PCR-RFLP AND MICROSATELLITE MARKERS
Qian Zhang, Standish K. Allen Jr, Kimberly S. Reece-2005
Marine Biotechnology 7 (6): 588 - 599
Abstract:

Genetic variation in wild Asian populations and U.S. hatchery stocks of Crassostrea ariakensis was examined using polymerase chain reactions with restriction fragment length polymorphism (PCR-RFLP) analysis of both the mitochondrial COI gene and the nuclear internal transcribed spacer (ITS) 1 region and using 3 microsatellite markers. Hierarchical analysis of molecular variance and pairwise comparisons revealed significant differentiation (P < 0.05) between samples from the northern region, represented by collections from China and Japan, and 2 of 3 samples from southern China. PCR-RFLP patterns were identified that were diagnostic for the northern (N-type) and southern (S-type) groups. Microsatellite marker profiles were used to assign each oyster to one of the two northern or two southern populations. Results for more than 97% of the oysters were consistent with the PCR-RFLP patterns observed for each individual in that oysters with N-type patterns were assigned to one of the northern populations and those with S-type patterns to one of the southern populations. At one site of the Beihai (B) region in southern China a mix of individuals with either the N-type or S-type PCR-RFLP genotypes was found. No heterozygotes at the nuclear ITS-1 locus were found in the sample, possibly indicating reproductive isolation in sympatry. Microsatellite assignment test results of the B individuals were also consistent with identifications as either the N-type or S-type based on PCR-RFLP patterns. The parental population for one hatchery stock was this B sample, which initially was composed of almost equal numbers of northern and southern genetic types. After hatchery spawns, however, more than 97% of the progeny fell into the northern genetic group by PCR-RFLP and microsatellite assignment test analyses, indicating that the individuals with the southern genotype contributed little to the spawn, owing to gametic incompatibility, differential larval survival, or a difference in timing of sexual maturity. Overall, results suggested that oysters collected as C. ariakensis in this study, and likely in other studies as well, include two different sympatric species with some degree of reproductive isolation.

(Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, VA 23062, USA; email of K. Reece: kreece@vims.edu)

MELANOPHORE DEVELOPMENT DURING METAMORPHOSIS IN PSEUDO-ALBINIC CLONE OF JAPANESE FLOUNDER PARALICHTHYS OLIVACEUS
Aiko Nakamura, Takahito Shikano, Akira Mizuta,Tadahisa Seikai-2005
Nippon Suisan Gakkaishi 71 (5): 729-735
Abstract:

A pseudo-albinic clone and control group of normal diploid in Japanese flounder Paralichthys olivaceus were examined from the larval stage to juvenile stage through metamorphosis on the differentiation process of melanophores in relation with pseudo-albinism. On the ocular side of the control group, the larger melanophores maintained their density from the larval stage through metamorphosis, but the smaller ones rapidly increased from the climax of metamorphosis (H-stage). On the blind side, the larger melanophores maintained their density but the smaller ones did not appear through metamorphosis. In the pseudo-albinic clone, both nearly complete and partial pseudo-albinism appeared at high percentages. In completely pseudo-albinic juveniles, the distribution of melanophores on the ocular side was similar to that on the blind side in the normal group, whereas the ocular side of partial pseudo-albinic juveniles had 3 types of distribution. Therefore, it was suggested that the appearance of small melanophores played a fundamental role in normal pigmentation on the ocular side, and the failure of this process inhibited normal pigmentation.

(Department of Marine Biosciences, Fukui Prefectural University, Obama, Fukui 917-0003, Japan)

RELATIONSHIPS BETWEEN GENETIC DIVERSITY AND NUMBER OF SUCCESSIVE GENERATIONS IN HATCHERY POPULATIONS OF AYU PLECOGLOSSUS ALTIVELIS ASSESSED BY MICROSATELLITE DNA POLYMORPHISM
Minoru Ikeda, Shuzo Takagi, Nobuhiko Taniguchi-2005
Nippon Suisan Gakkaishi 71 (5): 768-774
Abstract:

We examined the genetic variation of one wild and eight hatchery populations of ayu Plecoglossus altivelis assessed by the microsatellite DNA polymorphism. All hatchery populations had persisted for a number of generations from F4 to F31. Six out of the eight had propagated without the introduction of any other stock, however, not a few wild individuals had been mixed with each parental stock of the remaining two hatchery populations through their generations. All hatchery populations even in the mixing populations showed lower genetic variation, i.e. the mean number of alleles (A) and average heterozygosity (He), than those of the wild population. Strong significant correlations between the number of successive generations and both indices of genetic variability could be approximated by a negative linear line in He, but by a negative exponential curve in A. This result suggests that A in hatchery populations reduces faster than He during their captive propagation. The significant homozygote excess was also observed at almost all hatchery populations, indicating that inbreeding could be promoted within hatchery populations. All results would be attributed to genetic drift and/or adaptation of the captive stocks to the culture conditions.

(Laboratory of Population Genetics Informatics, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, 981-8555, Japan)

PROCESS OF TRUE AMBICOLORATION IN LARVAL AND JUVENILE JAPANESE FLOUNDER PARALICHTHYS OLIVACEUS: AN ULTRASTRUCTURAL STUDY
Yutaka Haga, Kei Nataami, Toshio Takeuchi-2005
Nippon Suisan Gakkaishi 71 (5): 782-790
Abstract:

This study investigated the process of true ambicoloration in larval Japanese flounder Paralichthys olivaceus induced by retinoic acid. Larvae at around F-G stages (TL 8.0±0.75 mm) were immersed in 50 nM all-trans retinoic acid for 5 days and reared until 60 days post hatch (dph) in order to develop true ambicoloration. Skin of fish was sampled every 4 days after immersion and subjected to ultrastructural analysis by transmission electron microscope. Melanophages started to be observed in the skin on the blind side of control fish at 30 dph. However, there were no melanophages in fish treated with atRA at 30 dph. In addition, larval type melanophores were observed under the subepidermal collagenous lamella in the skin on the blind side of fish treated with atRA. Only irridophores existed in skin on the blind side of the control fish at 40 dph. However, all three kinds of chromatophore existed on both sides of the skin of fish treated with atRA at 40 dph. These results suggested that the developmental process of pigmentation on the blind side of fish showing true ambicoloration mimicked that on the ocular side.

(Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 East Pratt Street, Baltimore, MD21202, USA)

OPTIMAL RELEASE STRATEGY OF HATCHERY-PRODUCED OCELLATE PUFFER TAKIFUGU RUBRIPE IN ARIAKE SOUND BY MARK-RECAPTURE EXPERIMENTS, BASED ON THE STOCKING EFFECTIVENESS FOR YOUNG-OF-THE-YEAR
Yasuharu Matsumura-2005
Nippon Suisan Gakkaishi 71 (5): 805-814
Abstract:

This study evaluated the stocking effectiveness of hatchery-produced ocellate puffer by sampling surveys at fish markets in Ariake Sound where young-of-the-year (YOY) puffer are landed. The recapture rate of released seeds (3-100 mm in total length) for each annual release in the three areas Shimabara coast, Isahaya Bay, and the innermost area of Ariake Sound was estimated at between 0.01 and 22.3%, and was found to increase with increasing release size and showed a tendency that the recapture rates of seeds released at Isahaya Bay and the innermost area are higher than that at Shimabara coast. The contribution rate of the released puffer to the total landings in number was estimated to range between 6 and 52%. Stocking effectiveness was shown in Fukuoka, Saga, Kumamoto and Nagasaki prefectures and the ratios of landing number and value differed among the release sites. It was suggested that 75 mm in total length is the optimal size for release and Isahaya Bay and the innermost area in Ariake Sound are the best sites for release in terms of the ratio of landing cash value to the cost of seed.

(Nagasaki Prefectural Institute of Fisheries, Nagasaki 851-2213, Japan)

SEX DETERMINATION IN FRESHWATER EELS AND MANAGEMENT OPTIONS FOR MANIPULATION OF SEX
Andrew J. H. Davey, Donald J. Jellyman-2005
Reviews in Fish Biology and Fisheries 15 (1-2): 37 - 52
Abstract:

Catadromous eels enter fresh water as sexually undifferentiated glass eels and develop into males and females before migrating back to sea as silver eels. Females develop ovaries directly from the ambiguous primordial gonad whereas males pass through a transitional intersexual stage before developing testes. Eels have sex-specific life-history strategies. Males may grow faster than females initially, but this difference is soon reversed and females attain a greater age- and size-at-metamorphosis than males. Male fitness is maximized by maturing at the smallest size that allows a successful spawning migration (a time-minimizing strategy) whereas females adopt a more flexible size-maximizing strategy that trades off pre-reproductive mortality against fecundity. Although heteromorphic sex chromosomes have been identified in some species, the sex of developing gonads is labile and gender is determined principally by environmental factors. Individuals experiencing rapid growth prior to gonad differentiation tend to develop as males, whereas eels that grow slowly initially are more likely to develop as females. Paradoxically, males tend to predominate under conditions of high density, which may be because a male “grow quickly, mature early” strategy increases an individual’s chances of survival during periods of intraspecific competition. High temperatures and saline conditions have also been proposed to favor development as males but experimental studies have failed to demonstrate a clear effect of either on sex determination. High proportions of female silver eels migrating from some upstream areas, lakes and large rivers may be due to low population density or poor conditions for growth in these habitats. Manipulating sex ratios in favor of females has the potential to increase eel production in aquaculture and to buffer natural populations against fishing pressure. Sex steroids (oestrogens and phytoestrogens) have a strong feminizing effect on undifferentiated individuals and are most effective when targeted at younger eels and administered at high doses for prolonged periods. Modifying local environmental conditions, in particular reducing eel density and limiting interference and social stress, may also promote the development of females. Further research into the timing and mechanisms of sex determination in eels is required to effectively and efficiently manipulate sex for conservation and/or economic benefit.

(National Institute of Water and Atmospheric Research, PO Box 8602, Christchurch, New Zealand; email of D. Jellyman: d.jellyman@niwa.co.nz)

EFFECTS OF DIFFERENT WATER TEMPERATURES ON THE HATCHING TIME AND SURVIVAL RATES OF THE FRESHWATER CRAYFISH ASTACUS LEPTODACTYLUS (ESCH, 1823) EGGS
Hamdi Aydin, M. Kamil Dilek-2004
Turkish Journal of Fisheries and Aquatic Sciences 4: 75-79
Abstract:

In this study, freshwater crayfish (Astacus leptodactylus, Esch, 1823) eggs were incubated starting seven weeks after spawning, at three different temperatures (11.8 ºC, 16±1ºC and 20±1oC) and the results were compared with respect to hatching time and survival rate. The eggs hatched between days 116 and 125, 88 and 97, and 69 and 74, at 11.8 ºC, 16 ±1 ºC, and 20 ±1 oC, respectively. The survival rates at these temperatures were 22.4%, 46.9% and 32.5%. In conclusion, it was found that A. leptodactylus eggs could hatch 1.5 months earlier than under natural conditions by increasing water temperature, starting in March, up to 20°C, but the optimum temperature for maximum hatching rate was found to be around 16°C.

(Kocaeli University, Gazenfer Bilge College, Department of Fisheries, 41670 Karamürsel, Izmit, Turkey; email of H. Aydin: aydin@kou.edu.tr)

ELECTRONICAL LARVICULTURE NEWSLETTER ISSUE 233 1 December 2005

ELECTRONICAL LARVICULTURE NEWSLETTER ISSUE 233
1 December 2005