Specificities of the structural, chemical, physical and sensory characteristics of the flesh are reviewed and related to different aspects of flesh quality. Potential for processing of catfish is high in terms of mechanization but rather low in terms of processing yields. The variability observed in body conformation traits supports the possibility to improve processing yields by genetic selection. Little is known on the structure of catfish flesh but a higher cohesiveness due both to greater connective tissue strength and probably a greater homogeneity of muscle tissues is observed, compared to other freshwater species. Although the presence of adipose tissues has not been demonstrated, intermuscular adipose tissues contributes with red muscle to lipid deposits in commercial size. Lipid content in catfish flesh increases with age but even at commercial size it is still lower than what is reported in other cultured fish. There is however a tendency in recent years for an increase in lipid content in catfish flesh due to increasedlipid content in the diet. Thus, further information on the control of lipid deposits is required in future especially in a view to improve taste and processing yields. The lipid composition of neutral lipids reflects that of the diet with high levels of monounsaturated fatty acids and a low w3/w6 ratio.Flesh colour is very subtle but it could be controlled either by the use of pigment supplementation in the diet or by rearing non pigmented catfish. Other physical characteristics of the flesh are very stable during the cooking process. Cooked flesh has a relatively low water-holding capacity and a low resistance to mechanical stress (compression, extrusion) thus contributing to the juiciness and tenderness of the flesh. The sensory characteristics of the flesh are somewhat neutral but consumers are able to detect thespecific characteristics of different species such as Channel catfish, African catfish and European catfish. Significant efforts to standardize the sensory evaluation of Channel catfish have been made in the USA but flavor and aroma of catfish seem to be more related to the fish itself than to other factors such as the diet composition. New data is available on off-flavors related to geosmin and methyl-iso-borneol. Specific control of the phytoplankton species which produce these compounds appears to be possible.Storage on ice affects the flesh acceptability as it does for other fish species, but catfish flesh seems to be stable at least physically during freezing. Traditional processing is used for preservation of the flesh. New processing methods have been tested for the diversification of catfish products or to produce substitutes for other animal products. Catfishes are generally shown to be suitable for processing.

The objective of this study was to identify a possible effect of food on the accelerationof decontamination in blue mussels, Mytilus edulis, containing diarrhetictoxins belonging to the okadaic acid (OA) structural group. An experimental protocol wasdesigned to describe and compare the decontamination kinetics and detoxification rates ofnaturally OA-contaminated mussels that had either received or not received food for threeweeks. The protocol was applied in two trials (in June 2006 and June 2007, called Ker06and Ker07), conducted one year apart on samples of mussels collected in the same area, atthe same season. Okadaic acid (OA), the main lipophilic toxin produced by the toxic algaDinophysis acuminata, was analysed over the course of thedecontamination, in hydrolysed (total OA) and non hydrolysed (free OA) digestive glandextracts, in order to estimate acyl-esters (7-O-acyl-ester derivatives ofOA) concentrations. OA analyses were also made for toxin presence in biodeposits and inthe aqueous phase. Bivalve physiological status was evaluated by biomass measurements (dryweight of flesh) and two biochemical compounds (total lipid and glycogen concentrations).Measured physiological parameters showed that mussels did not suffer under experimentalconditions. Both trials showed that the food accelerated the elimination of free and totalOA. This effect cannot be attributed to a dilution of the toxin in the tissue, as resultsexpressed in toxin burden led to the same conclusion. The kinetic models ofdecontamination differed between the two experiments: the model was linear for Ker06,provided that the values corresponding to the first two days were discarded, whereas datafitted a decreasing exponential curve better in Ker07. Detoxification rates increased asthe food supply increased. After three weeks of experimentation, the detoxification ratesfor total OA in Ker06 and Ker07 were 52 and 61%, respectively, in unfed mussels and 90 and89% in fed mussels (with the highest level in Ker07). Comparisons between the free OA andesters showed that detoxification rate was higher for free OA than for esters, whateverthe level of food supply. The results of this study suggest that food increase probablyaccelerates elimination of OA and OA-esters but the latter are eliminated at a lowerspeed.

Turbot juveniles (45 g) were exposed for 41 d (17 °C, 34‰ salinity) to constant normoxic (100–100% air saturation, 100–100) or moderate hypoxic (75–75% air saturation, 75–75) conditions and to repeated hypoxic shocks (20% saturation for 1 h, 5 d per week) from normoxic (100–20% air saturation, 100–20) or moderate hypoxic (75–20% air saturation, 75–20) conditions. A normoxic group was feed restricted (100-FR). Mass increase of 100–100 and 75–75 groups fed to satiation was not significantly different. In comparison, it was significantly lower in the 100–20 and 75–20 groups (NS between the two hypoxic shocks groups). Intermediate results were obtained in the 100–100-FR group. The lowest mass increase under hypoxic shocks was explained by a significant decrease in both feed intake and food conversion efficiency (FCE). FCE was lower in the two hypoxic groups, but only the 75–20 group was significantly different from all the other groups. There was no sign of stress and no change in the physiological status of fish in any group. When challenged, pre-conditioning of turbot to regular hypoxic shocks extended survival time, slightly but significantly, for 50% of the population. It was 8 h longer in starved than in fed fish. When reared for 1 year in normoxic water, the growth rate of post-challenged survivors was dependent on pre-conditioning: day 0–375 specific growth rate was significantly higher in the two groups acclimated to repeated hypoxic shocks. In the second experiment, it was shown that exposure to 20% air saturation for 12 h led to major physiological changes within 4 h: a significant decrease in plasma total CO2 and increase in plasma lactate contributing in maintaining blood pH stable, and a significant increase in osmolarity and chloride concentration. When returned to normoxic water, the recovery capacity of the fish was high: plasma osmolarity and total CO2 returned to pre-exposure levels within 1 h. The results are discussed in terms of turbot capacity to cope with repeated hypoxic shocks and to acclimate.

During 84 days, the effects of density on juvenile sea bass (Dicentrarchus labrax) (76±16 g) were studied in an experimental tank-based flow through system. Performance, stress response and resistance to virus infection were analysed under five stabilized rearing densities: 10, 20, 40, 70 and 100 kg m-3. Water quality parameters (CO2, total ammonia nitrogen and O2) were measured and maintained close to the recommended values for farmed sea bass by adjusting water renewal exchange. No significant differences were observed between density treatments, neither on stress response (cortisol) nor susceptibility to nodavirus. With regards to biological performances, the daily feed intake and specific growth rate were significantly lower in fish reared at the 100 kg m-3 density. Results on the effects of density in sea bass reared in flow through (present study) and in recirculating aquaculture systems (RAS) (Sammouth et al. 2009) were compared as a contribution to the identification of density not affecting health and welfare in farmed sea bass.

Results on changes in the total amino acids (protein bound + free) and the free amino acids (FAA) in relation to development, from egg (unfertilised and/or fertilised) to yolk-sac resorbed larva, before first feeding, in two Percichthyid fish, trout cod, Maccullochella macquariensis and Murray cod. Maccullochella peelii peelii, which lay demersal, adhesive eggs, are presented. Throughout development, the FAA accounted for only a small proportion (0.19% in fertilised eggs of both species) of the total amino acid pool. Nine essential amino acids (EAA) and eight non-essential amino acids (NEAA) were quantified in the amino acid pool at all stages of development. In both species, the total amino acid content decreased during the transformation (at 20 ± 1 °C) from newly hatched larva to yolk-sac resorbed larva. Overall, the changes in the TEAA and TNEAA reflected that of the amino acid pool. In trout cod, all but one EAA (lysine) and two NEAA (cysteine and glycine) decreased with ontogeny, from fertilised egg to yolk-sac resorbed larva. In Murray cod, however, the exceptions to the general decline were two NEAA (aspartic acid and glycine). In contrast, the FAA increased with development, the changes being reflected in both FEAA and FNEAA. Qualitatively, the predominant free amino acids in trout cod and Murray cod eggs were alanine, lysine, leucine and serine. Because the egg protein and the total amino acid contents declined with development, it is concluded that the rate of breakdown of yolk protein was higher than the anabolic and catabolic processes during embryogenesis. Data also suggest that in freshwater fish FAA are an unlikely primary energy substrate during embryogenesis.

A protocol for the incubation of Centropristis striata ovarian follicles in vitro from females that spawn repeatedly under laboratory conditions was developed. Isolated follicles underwent maturation after 15–24 h of incubation at 25 °C in 75% Leibovitz L-15 medium, containing relatively low doses of human chorionic gonadotropin (hCG) or homologous pituitary extract (50% response with approximately 2 IU/ml and 0.02 pituitary equivalents/ml, respectively). During maturation in vitro, follicles underwent a remarkable volume increase (about 340%) that was correlated with proteolysis of primarily the largest yolk proteinin the oocyte. The maturation response of follicles to hCG was size-dependent within a range from 400 to 600 m in diameter, with a maximum response displayed by 530–600 m follicles. The response of these follicles to hCG was not inhibited within a range of incubation temperatures from 15 to 28 °C, but the length of time required for the follicles to achieve 50% maturation was negatively correlated with increasing temperatures (r2 = 0.97; p ≤ 0.01). However, the largest follicles (530–600 μm) did not undergo maturation in response to high doses (1 μg/ml) of the major maturation-inducing steroids (MISs) known in teleosts, 17.20-dihydroxy-4-pregnen-3-one (17.20β) and 17.20β.21-trihydroxy-4-pregnen-3-one (20βS), even after a previous incubation period of follicles with 10 IU/ml hCG for 1.3 or 6 h. These observations indicate that C. striata follicles are very sensitive to increasing doses of gonadotropin, and that their responsiveness to this hormone is highly size-dependent within a very narrow range. The preliminary results also suggest that 17.20β and 20βS are not the MIS in this species.

Dietary nitrogen and phosphorus utilisation were evaluated in rainbow trout, Oncorhynchus mykiss, fed fish meal and soy protein concentrate-based diets. Two short term trials were conducted with rainbow trout having initial mean weights of 24 and 156 g maintained at a water temperature of 17 ± 1 °C, during which triplicate groups of trout were fed the respective diets two times a day to apparent satiety by hand. In both trials, fish fed fish meal-based diet exhibited significantly higher growth. In small trout, feed/gain ratio and protein utilisation were slightly higher in groups fed the fish meal-based diet; however, in larger fish, there was no significant difference between treatments. Nitrogen retention and loss were not affected by dietary treatments, while phosphorus retention was higher in fish fed diet containing fish meal (30 and 17 %) than in fish fed diet containing soy protein concentrate (25 and 15 %) and greatly reduced in larger fish. Phosphorus losses were 10 and 13 g·kg gain−1 of fish fed the fish meal-based diet, while those for fish fed the diet without fish meal were 14 and 17 g.

Changes in the total amino acid (TAA) and the free amino acid (FAA) contents during embryonic development, through newly spawned eggs, to pre-settled larvae of blacklip abalone (Haliotis rubra) are described. The TAA (protein bound + free) and the FAA contents increased prior to hatching but decreased towards settlement, but the changes were not always significant between different stages of development. Threonine, arginine, lysine and leucine accounted for nearly 50 % of the total essential amino acids (TEAA) in all developmental stages. The mean FAA content of newly spawned eggs was 262.8 ± 28.2 pmol·ind–1 and accounted for 11.5 ± 8.3 % of the TAA. Free essential amino acid (FEAA) content increased significantly as development progressed (P < 0.05), in which threonine, arginine and lysine accounted for over 63 % of this pool. In all developmental stages, the FAA pool was dominated by the non-essential amino acids taurine + proline which accounted for 79.5 % of the total. Generally, the FAA accounted for between 10 to 15 % of the TAA in the different developmental stages of blacklip abalone. All evidence appears to indicate that in blacklip abalone the energy requirements during early ontogeny are mostly met with from the lipid reserves, and that there is a tendency to conserve amino acids until pre-settlement.

The common whelk Buccinum undatum (Neogastropoda, Buccinidae) iswidespread along the north Atlantic coasts of France. In west Cotentin (Normandy), animportant local fishery exists that depends exclusively on this marine resource andrepresents about 90% of French whelk production. Despite successive restrictive measures,fishing yields have decreased since 2000. Shell length frequency distributions ofBuccinum undatum caught in west Cotentin were studied in 2005(N = 2910), in 2007 (N = 2032) and in 2009(N = 4145) ranging from 7 to 85 mm. In order to preserve this fisheryand to characterise the whelk stock at this site, the reproductive biology of this specieswas studied in relation to age, sex and size, for whelks of commercial size (45 to 61 mm)over the complete annual cycle in 2008. Age was determined by reading the number ofoperculum striae: animals between 45 and 59 mm had 2 to 4 striae. Four reproductive stageswere defined for males and females on the basis of histological analysis. The time courseof reproductive events was described according to size and sex: the highest percentages ofripe stages were found in October for both sexes. Spawning events occurred between Octoberand December. The shell length that corresponded to 50% of animals having mature gonads(49 mm and 52 mm for males and females, respectively, corresponding to 3 and 4 years oldanimals) exceeded the minimal landing size (45 mm). Fifty percent maturity was reached formales in their third year and for females in their fourth year. Reproductive investmentwas evaluated by quantitative analysis of the gonadal thickness or surface and was foundto be proportional to shell size. We found that less than 20% of females under 49 mm inlength were sexually mature and that these produced only a few eggs. This information,collected in a major fishing area, should assist fishery management decisions.

Fisheries management in the future will require that biological assessments be combined appropriately with operational, social, and economic considerations toward effective management of complex fisheries systems. This is not currently being done in fisheries management because of: (i) the lack of a conceptual and organizational framework for integrated and participatory decision making, and (ii) the lack of more appropriate methodologies for dealing with diverse sources of information, interdisciplinary objectives, and the inherent uncertainty of these systems. An integration of traditional "fisheries science" with other aspects of "fisheries management" and the field of "management science" in a new discipline of "Fisheries Management Science" is proposed. FMS is defined as "the rigorous application of the scientific method of problem solving in the development of strategic alternatives and their evaluation on the basis of objectives that integrate biological, economic, social, and operational factors into management decision making". Management science or operational research provides guidance in methodologies for complex decision making and problem resolution. A multidisciplinary decision framework is proposed involving the following key steps: (1) specification of quantifiable objectives and constraints; (2) modelling of the expected multicriteria performance of a range of proposed management decisions; (3) risk assessment through descriptions of the expected variability in performance measures; (4) risk management through analytical evaluation of risk and ranking of alternate solutions; and (5) continuous monitoring and improvement of past decisions including deviations from expected performance and corresponding adjustment of future alternatives toward achieving strategic objectives.

Proteases and protease inhibitors were detected in the seminal plasma, blood plasma, skin mucus and spermatozoa. Their molecular weights were estimated using SDS-PAGE under non-reducing conditions. The results demonstrate that the two main bands of anti-proteinase activity (APA) detected earlier in common carp seminal plasma with molecular weight of approximately 47 and 58 kDa are also present in other fluids. The intensity of staining was highest in blood and seminal plasma. The intensity in skin mucus was visible, but in a sperm extract it was faint. An additional fast migrating band (30 kDa) was observed only in seminal plasma. Highest APA was found in blood and seminal plasma followed by skin mucus. The activity in sperm extracts was low. The two serine-like proteases with molecular weight of 79 and 189 kDa in seminal and blood plasma have also been found. In skin mucus, protease of 79 kDa was also present. Metalloproteinases with molecular weights of 61 and 69 kDa were found in seminal and blood plasma but metalloproteinases of 44 and 38 kDa were observed only in seminal plasma. Although metalloproteinases, of molecular weight ranging between 61 and 75 kDa, were also visible in a sperm extract, the experimental approach used in this study did not allow unequivocal identification of unique proteases of spermatozoa. Blood plasma contains a serine protease and protease inhibitor not present in seminal plasma. Skin mucus also showed the profile of three unique proteases (two EDTA stimulated and one metalloproteinase). These results indicate that the analysis of proteases and their inhibitors makes it possible to distinguish contamination of milt with either blood or skin mucus. The physiological role of the detected protease-inhibitory system in fish seminal plasma is still unknown. It is possible that the protease inhibitor and proteases, unique for seminal plasma, are involved in a specific function of milt or testis (e.g. the control of spermatogenesis).

Apparent digestibility coefficients (ADCs) of macro- and micronutrients and energy of two diets were measured with common carp Cyprinus carpio reared at two water temperatures (18 and 25 °C). Two diets containing either soy protein concentrate (SPC) or Norwegian herring meal (FM) as a major protein source were formulated. Dicalcium phosphate was incorporated at a level of 4 % of the former diet. Duplicate groups of 20 fish (body weight: 55 g) were fed by hand twice a day to apparent satiety. After a 7-day conditioning period, faecal collection was made over 10 days using an automatic faeces collector. ADC of dry matter was not different (P > 0.05) between fish fed the two diets at 18 °C, but at 25 °C, we observed a higher ADC value in fish fed the FM diet than in those fed the SPC diet. ADC of protein was higher in fish fed the SPC diet than in the FM groups at either temperature. ADC of lipids was not different between the two groups at 25 °C but was found to be higher in fish fed the SPC diet than in the FM group at 18 °C. ADCs of energy and ash of the two fish groups remained constant at both water temperatures. Availability of phosphorus was significantly higher (P < 0.05) from fish meal based diets than from SPC based diets at both temperatures. A more striking effect of dietary protein source was found in the availability of calcium, which was lower in carp fed SCP based diets.

The use of genetic, biochemical and electronic markers in population biology and ecology has been growing tremendously during the last two decades. The first part of this paper aims at reviewing the main principles and advances of these individual markers through a few key applications on exploited marine fish populations. The second part is more prospective and investigates some possibilities that could arise in the near future through: (i) the development of new markers, (ii) the combination of different markers and (iii) the combination of quantitative approaches -whether classical or new- with individual markers. It is finally stressed how crucial individual markers will be to unravel the biocomplexity of wild fish populations and the key role they should play in the implementation of the ecosystem approach to fisheries.

We conducted displacement experiments using acoustic tags to study the orientation abilities of dolphinfish (Coryphaena hippurus) around FADs. Eleven fish were passively monitored using coded transmitters and acoustic receivers attached to FADs, while seven others were actively tracked with a vessel using continuous acoustic tags equipped with pressure sensors. All these 18 dolphinfish were captured close to a FAD and released between 70 and 1720 m from it. Five fish out of the 14 that were displaced at more than 360 m from a FAD (estimated detection range of our acoustic receivers, defining the target area during our experiment) returned to the target area. With one individual successfully returning to the target area after having been released at 1600 m from the FAD, the rate of return of fish released up to this distance was significantly higher than expected if they were moving at random, but many fish released at intermediate distances moved in other directions. Based on detailed statistical analysis of the return score, we estimated that dolphinfish are able to orientate towards a FAD area from at least 820 m. The connection between our definition of the target area and the association area of dolphinfish around a FAD is discussed, as well as the impact of stress and motivation in the rates of return observed. More experiments should be conducted to improve this first estimate. Specific experiments should also be designed to more accurately determine the association range of fish around FADs and their motivation to orientate towards FADs.

Interdecadal versus interannual time-scale variations of catch data of three anchovy fisheries distributed in the Humboldt Current System (HCS) were analyzed during the period 1960–2002, by using first a loess smoother. The loess residual data were considered as the interannual variation. Interdecadal changes were highly coherent for the three fisheries of anchovy distributed in the HCS, while there were differences in terms of interannual variations. The north-central Peru fishery was similar to the south Peru-northern Chile fishery in terms of the interannual component of fluctuation of these fisheries which was significantly and negatively related with El Niño-Southern Oscillations events occurring during the spring of the previous year. Interdecadal synchronous variations in the three anchovy fisheries suggest a common forcing by long-term environmental factors in the HCS, although other causes cannot be excluded. During the last 40 years, coherent changes in anchovy fisheries were observed, and this synchronous pattern is out of phase with large-amplitude sardine regimes. Long-term climate variability seems to be the main cause for interdecadal fluctuations in anchovy fisheries in the HCS, although available time series are too short to prove this link and exclude the hypothesis of nonenvironmental forcing. Large-amplitude regime shifts may be more important to consider than interannual changes since they can affect simultaneously and more dramatically the three anchovy fisheries distributed in the Humboldt Current System.

When discards data are included in fish stock assessments, it is generally assumed that all discarded animals die. However, there are fisheries in which a significant fraction of discards are able to survive. This case can be treated with a simple extension of the usual analytical model of exploited populations, enabling Virtual Population Analysis (VPA) to be used for parameter estimation. The paper examines the effects on estimates obtained by VPA when discards are allowed to survive, and validates a procedure for deriving partial fishing mortalities in multiple-fleet fisheries where discarding and survival rates are fleet specific.

Standard geostatistical techniques provide effective methods for estimating the global abundance and precision of a variable of interest, for mapping its spatial distribution and for describing its spatial structure. In the case of acoustic survey data, however, obtaining a measure of precision of the global abundance estimate is confounded by the combination of variances from the interpolation of both the acoustic data and the concomitant fish length data. Even if the global estimation variance could be calculated, the distribution of the estimation error is not known and so confidence intervals cannot be determined. Furthermore, kriged distribution maps, in minimising the estimation variance, tend to smooth out local details of the attribute’s spatial variation: small values can be overestimated and larger ones underestimated, such that the kriged map is smoother than reality. This can lead to serious shortcomings when trying to detect patterns of extreme attribute values, such as the high densities encountered in some fish schools. Stochastic geostatistical simulations, conditional on sampled locations, provide a solution to many of these problems. They can deliver a measure of uncertainty for local (density) estimates, a confidence interval estimation for the global mean density, and finally, reproduce global statistics, such as the sample histogram and variogram. In so doing, they also provide maps of the attribute, which are spatially realistic because the variogram is reproduced; these are generated as a number of equiprobable realisations. In the present paper, we apply these techniques to acoustic data from an acoustic survey of North Sea herring. Sequential gaussian simulations are used to generate realisations for fish length and values of the nautical area scattering coefficient. These are then combined to produce realisations of herring density. The combined set of multiple realisations is then used to provide confidence intervals for the global abundance estimate: 95% of the herring abundance estimates are between 5677 and 6271 millions of individuals. Although the method presented in this paper contributes to the assessment of total uncertainty for acoustic surveys, the approach may have suffered from bias due to the use of off-the-shelf data transformation algorithms on fisheries acoustic data, which are often very positively skewed. We discuss this limitation and propose corrections for future work.

The effect of feeding time was studied in rainbow trout fed different dietary levels of fat. Fish were fed either 1 h after light on in the morning or 1 h after light off in the evening with a low energy diet (LE, 6 % lipid) or a high energy diet (HE, 23 % lipid). Regardless of the diet, apparent digestibility and post-prandial protein synthesis were higher in fish fed in the morning than in those fed at the beginning of the night. In fish fed the LE diet in the morning, growth performance and nutrient retention efficiency tended to be higher than in those fed at the beginning of the night. In contrast, fish fed the HE diet in the morning had lower protein growth rate, protein content and protein retention efficiency than those fed in the evening. These results suggest that protein metabolism might be involved in the effect of feeding time on growth and that there is an interaction between the time of feeding and dietary level of fat on growth.

Fisheries exploitation systems are characterized by reciprocal interactions between fisheries activity and the harvested resource. Variability and changes affecting ‘natural’ and ‘socio-economic’ environments generate non stationarity of the variables used to describe the fishing activity, the resource and the yields. This characteristic needs to be taken into account in describing the evolution of the relationships between those variables, and in describing fisheries adaptability and sustainability. We present a dynamical system model with an application to data from surveys on activity and results of the Senegalese artisanal fishery from 1974 to 1992. A fitting procedure is proposed, giving estimates of the parameters of the model. A simulation is then made with the fitted model in order to apraise possible impacts of various events of different kind.

Face to the increasing anthropogenic disturbances that affect coral reef ecosystems, it becomes urgent to define appropriate ecological indicators for monitoring purposes. One useful approach is to search for a simplified description of the structure of biological communities that are highly diverse and complex on coral reefs. To this end, we propose to represent the trophic structure of coral reef fish assemblages by using fractional trophic levels assigned to each fish species. Fish abundance trophic spectra (i.e., the distributions of fish abundance per trophic level) were established for the fringing reefs of two bays located in the city of Nouméa (New Caledonia). The comparison of these trophic spectra revealed a similar trophic structure in the two bays, in spite of contrasted levels of fish abundance due to habitat damages. The embayment degree was characterized by changes in the fish trophic structure, reflecting a decreasing influence of urban and industrial wastes discharged in the bottom of the bays. This case of study shows the interest of using fractional trophic levels for the description of highly diverse biological communities. The trophic level-based approach offers new prospects in the search for ecological indicators, by characterizing the structure of biological communities by trophic signatures which testify to the disturbance level affecting their environment.