The cladocerans Moina micrura and Diaphanosoma excisum and the copepod Thermocyclops decipiens were studied in microcosms (0.8 m3) under semi-controlled experimental conditions at 25–29 °C for 32 days, by daily sampling after an initial monospecific inoculation. For each species, the time series began with an exponential population growth phase. M. micrura showed a higher daily population growth rate (mean = 1.19) than D. excisum (0.78) and T. decipiens (0.45). The growth phase of M. micrura coincided with bacterial and phytoplanktonic peaks while the growth phase of the two other species followed these peaks. After this phase, M. micrura quickly disappeared (day 10), while D. excisum biomass decreased but showed a second increase, followed by a stabilization sequence. T. decipiens biomass had a slower increase and stabilized after day 17. The passage to sexual reproduction in relation to crowding was the main regulating factor for M. micrura, whereas food limitation was important for D. excisum. For T. decipiens, population growth was limited by decreased recruitment to copepodite stages which could have resulted from cannibalism exerted by older stages.

The final phase of spawning migration of eight adult male Atlantic salmon, Sulnio solar L., was analysed by radio-tracking in relation to sea age and size in a spawning tributary of the Kiver Sélune. Four grilse and four multi sea-winter fish, one of which as a previous spawner, were radio-tagged and released. Their fork length ranged from 602 to 882 mm. The daily movement in the first two days alier release and the furthest upstream distance recorded from the trap during the study period were independent of fish length. Maximum amplitude of movement observed over the entire study period was inversely correlated with length. Daily movement decreased in all males during the spawning period and was negatively correlated with the size of fish. Surviving males remained in the vicinity of the spawning grounds after spawning. It was concluded that the length of male seemed to influence its behaviour in the last phase of the spawning migration, enabling a much more successful participation of the larger males in spawning.

L'étude du déterminisme du pré-recrutement de Pecten maximus (L.) en baie de Saint-Brieuc a été réalisée par captage de post-larves sur des collecteurs artificiels, et par échantillonnage benthique des juvéniles de coquille Saint-Jacques et de la macrofaune épigée et endogée superficielle. Les techniques mises en œuvres fournissent des estimations fiables de l'abondance des pré-recrues et de la force d'une classe d'âge, dès les quatre premiers mois de vie benthique. L'abondance d'une classe d'âge pré-recrutée est déterminée par la fécondité des adultes, l'hydrodynamisme (courants; turbulence à l'interface eau-sédiment), la nature sédimentaire des fonds (degré d'envasement; substrats disponibles), la température hivernale des eaux, l'intensité des interactions biotiques (compétition; prédation), et par les facteurs régulant la croissance du groupe d'âge 0 (la survie lors du 1er hiver est fonction de la taille des juvéniles). Les trois années d'étude montrent l'existence d'une forte variabilité spatio-temporelle intra- et interannuelle des mécanismes régulant l'abondance du pré-recrutement de Pecten maximus.

Variations in fish communities of shallow lakes in the Yangtze basins were investigated from September 2007 to September 2009. Six lakes were chosen for comparative study of species composition and diversity in relation to environmental variations. Lake heterogeneity was described with environmental physico-chemical variables, using principal component analysis. Sixteen families, composed of 75 species of fish were found in the studied lakes, Cyprinidae being the dominant group. Fish species were divided by habitat preference and trophic guild: benthopelagic and herbivorous fish were the most common guilds in all lakes. Species diversity and richness were significantly higher in spring, while the evenness, expressed by equitability of Simpson’s index, was not significantly different among seasons. Species richness and diversity were significantly higher in vegetated lakes (e.g. Liangzihu Lake) than in non-vegetated lakes (e.g. Biandantang Lake), with the largest area (Liangzihu Lake) harbouring the largest species richness and the greatest diversity. The relationship between environmental variables and fish assemblage were analysed using canonical correspondence analysis (CCA). The dominant gradients describing species composition and abundance among the sampling sites were: total phosphorus, total nitrogen, chlorophyll a, transparency and water depth. Our study led to the following conclusions: 1) the water quality was better - i.e. high transparency, low total phosphorus (TP) and total nitrogen (TN) and chlorophyll a- in vegetated lakes than in unvegetated lakes; 2) vegetated lakes had higher fish diversity than unvegetated lakes; 3) fish relative abundance (CPUE: number of fish per fishing pass) was significantly related to water chemical parameters. Consequently, the details of the findings are useful and relevant for developing suitable conservation strategies to sustain the integrity of fish communities in these lakes.

Vitellogenin (VTG) was isolated from the haemolymph of Penaeus vannamei by a three stepprocedure including ultracentrifugation, gel filtration and ion exchange chromatography. VTG wasused to raise polyclonal antibodies that were purified by ion exchange chromatography. A two stepcompetitive assay was developed in which VTG could be quantitated by its capacity to inhibit thebinding of antibody to the VTG previously adsorbed onto a solid phase. Sensitivity from equilibriumand from non-equilibrium assays was 41 and 2.3 ng/ml respectively. Estimates of within-assay andbetween-assay variabilities of standard curves were 4.2 and 9.6% respectively. The inhibition curves for dilutions of haemolymph from vitellogenic females, egg yolk extracts and purified vitellin (VTL) were parallel to the standard VTG curve, haemolymph from immature females and males showed no cross-reactivity. The antibodies directed against VTG recognize but partially VTL as shown by displacement curves. Recovery tests were near 100%. Thus the procedure was considered to be suitable for the measurement of haemolymphatic VTG. The VTG enzyme-linked immunosorbent assay (ELISA) developed in this study was validated by detecting physiological VTG changes in female shrimps after being fed squid extracts.

The nuclear DNA content in Dicentrarchus labrax, Sparus aurata, Liza ramada, and Anguilla anguilla, was measured by flow cytometric analysis. Male human leukocytes were used as internal reference cells. Nucleated fish erythrocytes were stained simultaneously to human leukocytes with a staining buffer containing propidium iodide (PI). Nuclear DNA contents of target species were estimated in relation to an assigned value of 7.0 pg DNA for male human leukocytes. The DNA content/nucleus (±CI) was 1.55 ± 0.02 pg for D. labrax, 1.90 ± 0.03 pg for S. aurata, 1.57 ± 0.02 pg for L. ramada, and 2.43 ± 0.04 pg for A. anguilla. Intraspecific DNA content variations ranged from 0-9% and averaged around 4% in all taxa. The results did not evidence significant differences in genome size between males and females in either D. labrax or L. ramada. / Anguilla anguilla

The change in catches and mean size of one-year-old perch (Perca fluviatilis) in Lake Geneva was studied between 1957 and 2005, and related to trophic changes and average temperature. The status of Lake Geneva, assessed on the basis of total phosphorus concentrations, switched from being oligotrophic before 1960 to eutrophic, with total phosphorus concentration reaching nearly 90 µg L−1 in 1976-1979. In response to management measures, the trophic status then returned to mesotrophy in the early 2000s. Zooplankton is the main food consumed by young perch, and quantities present (annual biovolumes of zooplankton) were recorded throughout the study period. The lake water temperature was also recorded. Data obtained from perch catches and perch spawns enabled eleven strong cohorts of perch to be identified. Strong cohorts dominated the stock for three years, until they were massively caught by fishermen. Yields have fluctuated widely, increasing rapidly until 1975, and subsequently decreasing, with an exceptional decline between 1976 and 1981. During the period 1977-1981, unfavourable climatic conditions in spring were probably the main cause of this fall in perch yields. For the other periods, perch yields and the mean size of one-year-old perch were significantly correlated with trophic parameters, total phosphorus concentration and zooplankton biovolume. Correlations are higher if only strong cohorts are taken into account. As a result of the re-oligotrophication process, perch growth has been progressively reduced, age at first maturity delayed and strong cohorts become less frequent; the mean size of 0+ individuals in strong cohorts is significantly smaller than in the other cohorts, suggesting a population density effect in the context of a limited supply of zooplankton. During the study period, trophic changes in Lake Geneva have had more impact on perch growth and yield than has temperature, since no significant correlation could be detected between water temperature and perch growth.

The sequencing of the human genome represented a watershed in the biological sciences. Post-genomic biology will be marked not only by vastly greater knowledge about the human genome and those of other species but will see an increasing application of novel and highly sophisticated technologies. Genomic strategies, together with those that look at the proteome of cells and tissues, are likely to revolutionize scientific research over the coming years. The ease with which novel and homologous genes can be isolated using the new databases and technologies, and the ability to study the expression of thousands of genes simultaneously at a global cellular level will be the major factors in this revolution. Genomic information is already being used to further our understanding of physiology and gene evolution in fish. Furthermore, the highly compact pufferfish (Takifugu rubripes) genome is being used extensively as a model to interpret those of tetrapods. Currently, studies of the fish genome are limited to gene evolution and to a much lesser extent, environmental toxicology. However, as interpretation of fish genomes gathers pace, we are likely to see the increasing involvement of other key areas such as reproduction, growth, pathology of disease, and flesh development/quality. Here, we present some of the advanced genomic technologies currently available and discuss how these might influence our knowledge of fish biology.

Quantitative real-time polymerase chain reaction (qPCR) is probably the most used method for gene expression quantification because of its high sensitivity and specificity. Nevertheless, this technology can undergo experimental errors and variations. Normalization of the results using a reference gene is therefore necessary to minimize these variations. As the study of immune genes in bivalve mollusks has increased in the last years, the establishment of adequate and stable reference genes for bivalves is strongly required. We analyzed the behavior of four putative reference genes: ribosomal RNA 18S, actin, elongation factor 1 − α and α-tubulin. The suitability of these four genes as internal control for qPCR was evaluated in mussel (Mytilus galloprovincialis) and clam (Ruditapes philippinarum) hemocytes after bacterial challenge. Four independent approaches (BestKeeper, GeNorm, NormFinder and DeltaCt ) were used to assess the suitable genes for stable expression. For these particular circumstances, the most stable gene in hemocytes was elongation factor 1 − α for mussels and α-tubulin for clams.

Cold shocks and hydrostatic pressure shocks, respectively, were applied for the induction of bothtriploidy and tetraploidy in the common carp. Cold shocks of 0-2 °C, lasting 40 minutes and starting 2–5 minutes after the activation of gametes and hydrostatic pressure shocks with 1-3-5 minute exposures at 49.03–56.88 MPa (i. e. 7 116-8 225 psi – pounds per square inch), starting 5 minutes after the activation of gametes gave the best results. The tetraploidy induction by cold shocks or hydrostatic pressure shocks resulted either in negligible (1.54%), or in zero yields, respectively. The applicability of particular types of ploidy manipulation and the standardization of shock initiation were discussed.

This review aims at comparing the fisheries management systems existing in New Zealand and in the European Union. The involvement of stakeholders at all stages of the management process is generally more transparent and better established in New Zealand than in the EU. Both systems aim at achieving an adequate balance between sustainability and utilisation and consider the precautionary approach as a founding principle. The socialobjectives are probably more explicit in the EU management system. In New Zealand, B MSY is a legal management target for all stocks in the quota management system (QMS), but management strategies were poorly explicituntil most recently. In the EU, there have not been any legal management targets or strategies until 1999. Since 1999, a number of multi-annual recovery and management plans have been established, including bothmanagement targets and strategies. Both management systems include conservation and access regulation measures. The EU management measures aim at regulating fisheries outputs and inputs, and discarding is tolerated. New Zealand management is almost exclusively output-based, and discarding practices are banned. In the EU, while individual quotas (IQs) are implicit in several countries, there is no consistent pattern across Member States for allocating TACs. In New Zealand, individual transferable quotas (ITQs) are implemented, and some flexibility in catch-quota balancing is provided by a carry-over allowance and the payment of a landing tax, the deemed value, for every fish landed above quota. If rights-based management were introduced in the EU based on, e.g., the New Zealand model, we suggest that concentration rules be set in accordance with the social objectives of the Common Fisheries Policy, and also that the deemed value should be set based on science and economics.

Managing adequately the exploitation of commercial species subject to technical interactions is a key step towards the ecosystem approach to fisheries. We evaluate here, using a bio-economic modelling approach building on the ISIS-Fish simulation platform, the relative impact of total allowable commercial catches (TACC) and of taxes applicable to over-quota landings (deemed value) on the sustainability of a selection of species exploited by the New Zealand hoki (Macruronus novaezelandiae) fishery. We investigate some aspects of the hoki mixed fisheries, consisting of four fleets and nineteen métiers, by considering the technical interactions between hoki and Southern hake (Merluccius australis). The dynamics of effort allocation were modelled using gravity model, using value per unit of effort (VPUE) as attractivity coefficient. Several management scenarios, based on different levels of TACC, effort limits and deemed value have been defined. The impact of these strategies on spawning biomass and catches has been investigated. The results confirm that the deemed value may, in combination with TACC, be anefficient management tool. By increasing the hoki deemed value, we could somehow limit the decrease in the hoki TACC needed to harvest Western hokisustainably. Constraining hoki fishing also restricts Southern hake fishing in the Chatham Rise and in the West Coast South Island, but leads to increased targeting of this species in the Sub-Antarctic area. The relative costs of renting/buying quota or paying the deemed value are most constraining when the hoki TACC is at relatively low level and when the hoki deemed value is more than 1.5 times the current value.

A fish aggregating device (FAD) called a payao is conventionally installed to catch pelagic species in the Philippines. The waters around the Philippines are important regions for yellowfin tuna stocks because they include spawning grounds and nurseries. To understand the schooling behavior of juvenile yellowfin tuna Thunnus albacares around a payao, 13 juveniles (20.5−24.0 cm fork length) double tagged with ultrasonic transmitters (V7-2L-R256; Vemco Ltd.) and data loggers (DST-micro; Star-Oddi Ltd.) were released around a payao. A self-recording receiver (VR2-DEL; Vemco Ltd.) was attached on the mooring rope of the payao to follow the horizontal movements and data loggers recorded the vertical movements of tagged juveniles. Nine juveniles were recaptured simultaneously by ring net at the same payao after 4-7 days. One juvenile was recaptured by hand line at another payao 12 km away from the tagging site after 6 days. Recaptured juveniles showed a diurnal schooling pattern suggesting different school shape and foraging strategy between daytime and nighttime. Juveniles showed a diurnal horizontal moving pattern, concentrated near the payao during daytime, while they were distributed around the payao at nighttime. The fluctuations of swimming depth were synchronized among fish. Juveniles also showed a diurnal vertical movement pattern in surface mixed layer. They concentrated in a shallow and narrow range (11.2±8.2 m, mean ± SD) at nighttime, while they were distributed to a deep and wide range (20.0 ± 11.8 m) during daytime. The maximum vertical neighbor distance indicated the vertical thickness of the school and showed a peak around noon. Higher vertical movement speed during daytime indicated vertical foraging in a water column, while at nighttime the juveniles might forage horizontally following the diurnal migration patterns of prey in the surface layer.

The aggregate backscattering cross-section, σag is the sum of backscattering cross-sections of all fish in a shoal. It is a basic acoustical parameter used for shoal description and biomass estimation. Simulations were undertaken for evaluating the impact of horizontal dimension, density, depth and beam width on measurements of σag for shoals with constant abundance. The important factor determining measurement bias is the ratio of shoal size expressed as along cross-section length relative to along ship beam width at mean shoal depth. The results show that 10 log10(σag) is underestimated by about 8 dB for a 5 m long shoal located at 200 m depth if detected by a 7° beam. A formula for correcting σag estimates for shoal sizes bigger than 1.3 times the beam width is proposed. The negative measurement bias can also be reduced by using transducers with narrower beam widths.

Water quality assessment is a key factor in the environmental management of freshwater networks, especially those including fish farms, which need cost-effective operational tools to monitor and control their waste output. In France, current legislation specifies limits in concentrations of dissolved compounds and suspended solids at fish-farm outlets. Despite the development of mass-balance modelling tools, chemical analysis of water (hydrological method) remains the most widely used method. To understand better the environmental impact of trout farms on aquatic ecosystems and to compare waste assessment methods, we monitored 20 commercial flow-through trout farms for 24 h, and we compared data obtained with the two methods (hydrological method and mass balance modelling) by linear regression. For total nitrogen and total phosphorus, the correlation between the two methods was high; thus, considering the uncertainty of both methods, this study was not able to determine which was more accurate. The high correlation between observed ammonia concentrations and predicted total nitrogen emissions provides a coefficient for estimating ammonia emissions at the farm level. The same approach is proposed for the evaluation of phosphate emissions. In conclusion, this study confirms the utility of simulation modelling for assessing nutrient release from fish farms.

Tetraploidy was induced in embryos of Ruditapes philippinarum by treating the eggs with cytochalasin B (CB). Two treatment times were found to be effective in inducing tetraploidy: 0 to 10 minutes after insemination (before formation of the first polar body) and 45 minutes after insemination (just before the first cleavage). Treatments, started 5 and 45 minutes after insemination, produced $64.4\pm7.8{\%}$ and $28.3\pm2.3{\%}$ tetraploid embryos, respectively, after 6 hours (on the average over 3 experiments). However, no tetraploids were detected in 4-month-old spat. Sperm entry delayed by the CB could be involved in induction of tetraploidy by early treatment.

We investigated the patterns of occurrence of FAD-associated fish off the coast of Sardinia, Sicily and Majorca (Western Mediterranean). Two working hypotheses are presented to test whether or not “differences exist in fish assemblages at i) the spatial and ii) the temporal level”. Quantitative and qualitative experimental data were obtained from a total of 521 censuses at 17 fish aggregation devices (FAD) using underwater visual observations carried out in Sardinia and Sicily in May-October 2001 and 2002 and a purse seine data set on 3 FADs obtained from a previous investigation carried out in Majorca. The results from the multivariate analysis rejected both hypotheses. In all locations, patterns of fish assemblages were dominated by Coryphaena hippurus, Naucrates ductor, Seriola dumerili, Balistes carolinensis and Trachurus spp., a pattern evident from examining data at bi-monthly intervals. When the most dominant species highlighted with similarity percentage (SIMPER) analysis were analysed with an analysis of variance (ANOVA), a time effect was clearly apparent and subsequently confirmed for four of these five species (B. carolinensis being the exception); the location factor was also found to be relevant (except for the genus Trachurus). We concluded that differences noted were principally due to the “time shift” in the occurrence of these species in the three locations, leading to the assumption that a relationship did exist between the gradual but significant shift in seasonal temperature and colonization at the study locations. Defining selected community structure indices was also important because no reference points are actually available for the pelagic environment in the Mediterranean Sea.

Over the past decades, pollution, overfishing, and habitat degradation have driven the population size of Taiwan shoveljaw carp down markedly in Taiwan. Cryopreservation is a useful tool which could be used to maintain genetic resources to protect and preserve this endemic species. Four cryoprotectants [dimethyl sulphoxide (DMSO), dimethylacetamide (DMA), glycerol and methanol] and six freezing rates (0.5, 1, 2, 4, 8, 16 °C min-1) were tested in order to develop an optimal controlled slow-freezing protocol for Taiwan shoveljaw carp spermatozoa. Samples were subsequently examined under the scanning electron microscope to reveal whether cryopreservation had affected their ultrastructural morphology. The highest survival rate (50.1 ± 2.0%) was observed with a freezing rate of 8 °C min-1 in 1M DMSO, using SYBR-14 + PI staining. Fertility and hatching rate results using frozen-thawed spermatozoa (90.2 ± 2.2% and 22.3 ± 2.5%, respectively) were not significantly different from results with fresh spermatozoa. After cryopreservation, 21.0 ± 1.6% of frozen-thawed spermatozoa had mid-piece swelling and rupture of the head. Cryopreservation might, therefore, slightly affect Taiwan shoveljaw carp spermatozoa in terms of morphological change. However, these alterations could be compensated by using large enough numbers of normally functioning frozen-thawed spermatozoa to achieve a standard equal to fresh spermatozoa. This is the first report of successful cryopreservation of Taiwan shoveljaw carp spermatozoa using a controlled slow-cooling method.

In the marine environment, small forage species can predate on, or compete with, the pre-recruits of their larger predators. The “cultivation effect” hypothesis proposes that this mechanism can slow down the recovery of depleted populations of large demersal fishes by creating Allee effects that lower their recruitment success. Using an individual based fish community model applied to the southern Benguela ecosystem, we simulate situations of potential cultivation effect on a population of shallow water hake Merluccius capensis. We search for evidence of Allee effects due to cultivation and investigate how complex trophic interactions could influence their underlying mechanisms and impact. The resilience of the shallow water hake population was measured by following the variations of the ratio R/S (the number of recruits over the number of spawners) when population size decreases and the predators and competitors of shallow water hake pre-recruits were identified. Simulations suggest that cultivation effects are likely to emerge within the fish community of the southern Benguela ecosystem. Our twelve species model emphasizes that cultivation effects result from complex influences of predation and competition on the different pre-recruit stages, whose trophic role depends on both body size and geographical distribution. For realistic linkages between forage species and shallow water hake pre-recruits, cultivation effects occurring in the limits of the southern Benguela fish community are predicted to delay population recovery by several decades. These significant delays are not characterized by a decrease of R/S at low stock size, which is the sign usually tracked when looking for Allee effects. Our study suggests that cultivation effects could play a major role in the dynamics of overexploited large demersal fish populations and pleads for the development of improved detection techniques for these processes.

The impact of toxic outbreaks of Gymnodinium catenatum, producer of paralytic shellfish poisoning toxins (PSP toxins) and Pseudonitzschia spp., producer of amnesic shellfish poisoning toxins (ASP toxins), was studied throughout the culture cycle of the king scallop Pecten maximus (length from 40 to 100 mm). Toxin concentration, in plankton and in the digestive gland of the scallops, other variables that describe the state of the cultured scallops (mortality, growth, length/weight ratio, gonadosomatic index) and the main environmental conditions (temperature and in vivo fluorescence) were determined from December 2001 to April 2003. Temperature ranged from 14 °C during the winter to 22 °C at the end of July. In vivo fluorescence ranged from not detectable to 25 relative units, with a maximum also recorded at the end of July. ASP toxin levels, in both plankton and organisms, were high during the first half of the sampling period (maximum 450 ng domoic acid L−1, in plankton, and 175 µg·g−1 of scallop digestive gland) when the scallops were juvenile. PSP toxins attained larger concentrations in the second half of the sampling period (maximum of 1.8 nmol L−1 in plankton and 550 nmol g−1 of digestive gland, of gonyautoxins after hydrolysis). Several mortality events took place during the period studied, but none of them coincided neither with an ASP or PSP outbreak nor with long exposure of the scallops to these toxins. One of the recorded mortalities occurred simultaneously with a high concentration of PSP in the scallops, but also with an important spawning. Additionally, it was not coincidental with the bloom of toxic plankton, thus, post-spawning stress seemed to be the main responsible for the mortality. No appreciable effect of ASP or PSP toxinson growth or reproductive state of the cultured scallops was found. Therefore, neither ASP nor PSP toxins appeared to represent a direct threat to the culture of Pecten maximus in that case.