Marine protected areas (MPAs) are increasingly being considered and used for the management of fisheries targeting mobile fish populations. Here, the recent modelling literature on MPA effects for mobile fish populations and their fisheries is reviewed. Modelling studies conducted since 2011 have filled a considerable number of knowledge gaps on the impacts of MPAs for species exhibiting home-range behaviour, nomadic movements or behavioural polymorphism, and on the effects of “targeted MPAs”, which aim to protect relatively small areas where migratory fishes spend an inordinate fraction of time or are highly vulnerable to fishing (e.g., nursery or spawning zones). Also, in recent years, two studies investigated the consequences of MPAs targeting highly migratory (tuna-like) fish populations for the first time in the history of MPA modelling. Recent modelling studies found that MPAs aimed at protecting mobile species may have positive conservation effects under a relatively wide range of situations, but may generate long-term fisheries benefits only under a very limited set of conditions. In particular, MPAs were not found to be beneficial for the fisheries targeting highly migratory populations. Strategies producing both conservation and fisheries benefits were identified, which depend on fish movement patterns and numerous aspects of fish life history and fisheries dynamics. However, in view of the diversity of fish movement patterns in MPA systems and current dynamics in resource management, it is clear that additional modelling work is needed to fully understand how protected areas affect mobile fish populations and their fisheries and to be able to implement pertinent MPAs. In particular, future modelling studies should systematically assess the effects of MPAs in relation to other management tools to find strategies that are most effective in meeting management objectives, and explore the impacts of “dynamic” MPAs that follow highly migratory fish populations in space and time.

Fisheries bycatches and discards constitute a significant problem in many fisheries worldwide. Unlike the pelagic purse-seine, the demersal purse seine usually targets high commercial value demersal species such as sea breams (e.g., Diplodus spp., Pagellus spp., Sparusaurata) and the European sea bass (Dicentrarchuslabrax), while discards consist mainly of pelagic species and juveniles of the above mentioned species. In order to evaluate the efficiency of a selectivity device in reducing bycatch and consequently of discards in a demersal purse seine fishery, experimental deployments were carried out. The bycatch reducing device (BRD) consisted in the use of a panel of diamond-shaped mesh netting of 70 mm stretched mesh in the posterior part of the purse seine. Data from 61 experimental fishing trials allowed the evaluation of discards, with Scomberjaponicus, Boops boops, Sardina pilchardus, Diplodus bellottii and Belone belone being the main discarded species. The mean discard ratio per set was 0.49 (± 0.30 standard deviation). The causes for discarding were also identified, with low commercial value being the most important reason. The results of the trials with BRD, were promising, with an average of 49% (± 24%) of the fish escaping per set, especially from those species that are most discarded. Overall, the use of this method for reducing discards can be considered positive for the following reasons: there is no need for structural modification of the fishing gear, the BRD is easy to deploy, and it is efficient in terms of species, sizes and quantities of fish that manage to escape. It therefore has significant benefits for the demersal purse seine fishery and possibly for other “métiers” as well.

Regular observation of survival of the carp breeding lines constituting a living gene bank at the Institute of Ichthyobiology and Aquaculture in Golysz (Poland) over a period of at least 15 years showed different survival rates for various lines. In this study, we have examined the polymorphism of the major histocompatibility complex (MHC) gene class II B in nine carp lines. The class II B gene encodes for the part of the MHC class II molecule which presents peptides from pathogens and protein antigens that are present in the extracellular milieu and have been taken up into the endocytic vesicles of antigen-presenting cells. Polymerase chain reaction was used to amplify Cyca-DAB gene fragments comprising part of exon 1, complete intron 1 and almost complete exon 2. Exon 2 encodes for the β1 domain which is the most polymorphic fragment of MHC class II molecules. Single-strand conformational polymorphism (SSCP) was applied to detect different MHC class II B haplotypes. The analysis revealed the presence of seven different haplotypes occurring with various frequencies.

The general characteristics of the main salmon (Salmo salar L.) stocks in the Massif armoricain (Brittany and Lower Normandy), in the Loire-Allier and in the Adour-Gaves-Nive have been summarized. Due to the poor quality of the previous fishing statistics, there is no clear picture of the historical evolution of the salmon stock. However, a dramatic decrease in the endemic range of Atlantic salmon in France can be shown since the mid-18th century and more particularly during the last 50 years. The lack of precise informations describing the size of the catches and the levels of exploitation at sea and in the estuaries make it impossible to estimate the impact that exploitation has led on the evolution of salmon stocks. The mean age of salmon in freshwater ranges from 1 to 1.5 years. The Loire-Allier basin is characterized by a relatively high proportion of large salmon (3 fish) in the rod catches. Fish native to Brittany and Lower-Normandy (Massif armoricain) have lover growth rates than those from the Loire-Allier and Adour-Gaves-Nice Basins. A greater proportion of the early grilse stocks (migration May-July) are males than compared with fish running later. The sex ratio of the multi-sea-winter salmon is biased towards females.

Un lot de 40 mâles d'une souche de truite arc-en-ciel (Salmo gairdneri) à reproduction printanièrea été suivi. Seuls les spermes d'un volume supérieur ou égal à 6 ml ont été caractérisés et congelés enboulettes. L'analyse factorielle des correspondances entre les caractéristiques et la fécondance dusperme après 5 à 9 mois de congélation a montré en particulier que l'aptitude à la cryoconservationpeut être caractérisée par l'analyse du plasma séminal : les spermes médiocres sont associés à uneosmolarité plasmatique élevée (260 m-osmoles) et/ou une teneur élevée en protéine 42 KD, l'un desconstituants majeur de la membrane des spermatozoïdes; les très bons spermes sont associés àl'absence de protéine 42 KD dans le liquide séminal. Ces résultats renforcent l'idée que l'aptitude à lacryoconservation du sperme de truite dépend en premier lieu de la qualité de la membrane des spermatozoïdes.

Changes in the fatty acid profiles of the Percichthyid fish trout cod, Maccullochella macquariensis (Cuvier), and Murray cod, M. peelii peelii (Mitchell), two Australian native freshwater fish species, were investigated during early development from egg to yolk-sac-resorbed larval stage. In the two Percichthyid fishes polyunsaturated fatty acids (PUFA) accounted for more than 50 % of the 19 quantified fatty acids in total lipid. The fatty acids that occurred in the highest abundance in both trout cod and Murray cod, in all developmental stages, in order, were docosahexaenoic acid [DHA 22:6(n-3)], arachidonic acid [AA 20:4(n-6)], oleic acid [18:1(n-9)] and palmitic acid (16:0), all of which exceeded 100 μg per mg total lipid in most instances. The ratio of 22:6(n-3) to eicosapentaenoic acid-20:5(n-3) in eggs of trout cod and Murray cod was 5.4:1 and 7.3:1, respectively, and remained almost unchanged through development, and was considerably higher than the 2:1 ratio generally reported for fish eggs. In trout cod, 11 of the 19 fatty acids in total lipid decreased during the transformation from egg to yolk-sac-resorbed larva. In Murray cod, only 16:1(n-7) showed a significant decrease whilst 20:4(n-6) increased significantly with development. Overall, there was a tendency in both species to conserve n-3 and n-6 series highly unsaturated fatty acids (HUFA), suggesting their essentiality in first feeding larvae. These observations are discussed in relation to the feeding habits of trout cod and Murray cod, which are top order, freshwater carnivores.

The mussel (Mytilus edulis) is successfully grown in aquaculture inEurope. Mussels are usually sold live and wet storage is becoming more common. In thisstudy, oxygen demand and ammonia excretion were assessed at increasing water temperaturesand different post-harvest situations. This information was used to calculate minimal flowrates per unit biomass of live mussels sufficient to keep oxygen above 5 mg L-1or 50% saturation, and avoid accumulation of ammonia in commercial wet storage. In thisstudy, rope-grown mussels were kept out of water for 8 h to simulate harvesting conditionsand then re-immersed in holding tanks at 5, 10 and 15 °C. Oxygen and ammoniaconcentrations were measured immediately after mussels were re-immersed (0 h), after 6 hand then every day for 3 days. After this period, the mussels were again kept out of waterfor 48 h to simulate long-distance transport and once again re-immersed for the sameperiod as before. In the first 6 h after re-immersion, the oxygen consumption was between7.5 and 12.2 μmol g-1 h-1 (dry flesh) and afterthis period it decreased to a standard level of around 4.0 ± 0.9 μmolg-1 h-1 and was independent of temperature. There were no majordifferences in oxygen consumption between mussels having spent 8 and 48 h out of water atany of the subsequent water temperatures used for re-immersion. In contrast, the ammoniaexcretion showed greater differences according to temperature and time out of water.Ammonia excretion was lowest at 5 °C (<0.01 μmol g-1h-1). The implications of these results for the industry and authorities arediscussed considering the water flow rate, depuration specifications and energy costs.

L'influence respective du sédiment et des populations d'huîtres cultivées (Crassostrea gigas) sur l'accumulation et le recyclage des différentes formes de l'azote organique et minéral sont précisées. Les flux d'azote minéral et organique des formes dissoutes de la colonne d'eau, des eaux interstitielles et des eaux susjacentes sont étudiés, ainsi que ceux des formes particulaires représentés par les matièresen suspension, les biodépôts et le sédiment. Le flux annuel de la colonne d'eau d'azote minéral est de 10,5. 106 g.m−2, celui de l'azote organique n'atteint que la moitié. Le flux d'azote particulaire est égal à 15.106 g.m−2.an−1. Par contre l'azote phytoplanctonique ne représente que 6 % de l'azote particulaire total. Ceci souligne l'origine détritique de la matiére organique de cet écosystème. Dans les zones de cultures, l'accumulation d'azote est de 94 g.m−2.an−1, alors qu'elle n'est que de 15 g.m−2 . an−1 dans les zones témoins. Les flux d'azote minéral dissous en provenance du sédiment sont plus élevés sous les cultures (23 g.m−2.an−1) que dans le sédiment témoin (15 g.m−2.an−1). Une culture d'huîtres induit une fixation supplémentaire d'azote de 71 g.m−2.an −1. Deux comportements saisonniers caractérisent cet écosystème : (i) de forts apports hivernaux de nitrates par la colonne d'eau et leur absorption au niveau du sédiment, accompagnés d'une forte production de biodépôts; (ii) un relargage printanier et automnal d'ammonium par le sédiment en présence d'azote organique abondant dans la colonne d'eau.

Ecosystem assessments of fisheries based only on survey data will often have to use surveys that were designed historically for special purposes, e.g. for assessing abundances of two or three target species, or for tuning VPAs. An important question then is whether the previously collected data can provide informative time series of abundance indices and other state indicators for a wider range of target and non-target species. Some potential shortcomings of existing data series are treated in this paper leading to four questions which can guide the user to determine the suitability of an existing time series: did the survey cover the stock of each species adequately? Did survey catchability vary significantly between length or age classes? Did survey catchabilities vary significantly in space or time? Was the sampling effort sufficient? Simple methods for investigating these questions are proposed and illustrated with examples.

A selection of ten uni- and multivariate, nonparametric statistical methods thought to be useful for assessing trends in indicators estimated from trawl surveys is described. Nonparametric methods make minimal assumptions about the data and can therefore be suitable when parametric modelling methods, as typically preferred by fisheries scientists, are not suitable. The various methods described are sensitive to a variety of specific features of a trend thereby allowing many different forms of variation over time to be identified, e.g. changes in level, sloping straight or curved lines, and differing cyclicities. In contrast, model-based investigations can be constrained in this regard if the single model which is adopted and fitted to the trend is a simplification of its form.

One of the main limitations in acoustic stock assessment is fish identification. We propose here a new method for identifying several communities of tropical fish within a surveyed area. This method, called "Acoustic Populations", consists in splitting a study area in systematic regular strata such as geographical rectangles, and calculating for each stratum a set of acoustic parameters that can be easily obtained with conventional acoustic equipment, and have a discriminant power, such as target strength, mean density, confidence interval and dispersion indexes. It is based on the fact that the biological (specific diversity, physiology) and ethological (gregarism, migrations, etc.) characteristics of fish communities have a particular influence on the echoes recorded, which become characteristical and thus are able to discriminate acoustically several populations. An example of application of the method is given for Eastern Venezuela, and the use of the results for mapping, evaluation and stratification of acoustic data is discussed.

Selective fishing pressure on more highly valued marine living resources is one of the key factors proposed to explain changes occurring in fish communities and associated landings of commercial fisheries. The aim of this paper is to establish the nature of changes in the landings of French fishing fleets operating in the Bay of Biscay in the period 1973-2002, and whether these changes could be related to the relative economic attractiveness of different fish species. The analysis focuses on trends observed in the landings of all commercial fish species over the last three decades. It is based on data of annual quantities landed and ex-vessel prices compiled from official French landings records, and on bio-geographical descriptors of these species derived from published data. Using simple index numbers and multivariate analysis, we examined changes in total landings in terms of their volume and value, as well as changes in their composition. We show that the composition of landings significantly changed over the study period, with an increase in the proportion of pelagic species, of lower economic value. The average ex-vessel price of production by the fleets tended to decrease from the late 1980s; partly due to a cross-species drop in prices, occurring mainly after 1993, but also to the increased proportion of low-priced species in the landings. This caused a significant drop in the total gross value of production in the second half of the study period.

Spatial closures are commonly used by Australian fisheries managers to alter fishing patterns. To evaluate different fishing closures, however, fishery scientists have to understand and model the spatiotemporal interactions between fish stocks and fishing fleets. We develop a deterministic, stationary, per-recuit, age-structured simulation model to assess different spatial closure strategies, and use date from the Torres Strait tiger prawn fishery, Penaeus esculentus, as a working example. Our results show that selection of an optimum spatial closure largely depends on the relative importance given to changes of the different utility functions evaluated (yield, value, egg production). We show that, on average, with a spatial closure yield-per-recruit would decrease, but also show that value-per-recruit may increase 10% with the appropriate closure. Our results suggest that egg-per-recruit would always increase in the presence of a closure. By incorporating parameter uncertainty within the simulation model we predict the uncertainty associated with alternative closure strategies, and thus provide valuable information for the decision-making process.

The purpose of this study was to determine biochemical changes occurring in blue mussels (Mytilus edulis) fed effluent from an Atlantic cod (Gadus morhua) aquaculture facility over a period of ten weeks, compared to those in mussels fed a commercial shellfish diet and those supplied only filtered seawater. The total lipid and fatty acid content (mg g-1 wet weight) significantly decreased for mussels fed effluent during the experiment. The only change in the lipid class composition (% total lipid) at the end of the experiment was a significant increase in the proportion of acetone mobile polar lipids. There were several significant changes in the fatty acid composition (% total fatty acid) including an increase in the proportion of 18:1ω9, 18:2ω6, 20:4ω6, 21:5ω3 and the dienoic non-methylene-interrupted fatty acids 20:2a and 22:2b and significant decreases in the proportions of 16:0, 18:4ω3 and 20:5ω3. The increase in non-methylene interrupted dienes suggests that the amount of essential fatty acids in the effluent may be insufficient for optimal mussel growth. The presence of the terrestrial plant marker 18:2ω6 in both the fish feed and the effluent and its increased proportion in mussels fed effluent suggest that this fatty acid may have potential as a marker for aquaculture wastes.

The bivalve’s aquaculture industry is an important component of the economy in Eastern Canada. Seed collection is an initial and critical activity in most bivalve aquaculture industries including mussel farming in Prince Edward Island, production is entirely dependent on natural spat collection. Although seed supply is not a concern from a quantitative standpoint, there are growing concerns about the quality of natural seed. The general objective of this study was to identify and assess mussel seed quality criteria on the basis of physiological and biochemical status under laboratory and field conditions. The performance, as estimated by metabolic measurements, lipid class composition, multi-locus heterozygosity (MLH) and survival to stressful environment of seed from 6 different stocks sources was first compared under laboratory conditions at 12 °C and 25 °C. Results showed that MLH varied among the six sources of mussels in a way which is consistent with the physiological and biochemical indicators of seed quality. Mussels from Shippagan (New Brunswick) and Tracadie (Prince Edward Island) were found to have the highest quality scores and the best adaptive capacity to extreme water temperature under laboratory conditions. The results of the stock-site reciprocal field studies are in general agreement with those of the laboratory experiments with higher survival of mussels from Shippagan, Tracadie and St. Peters Bays in the various study sites. Our results suggest that the measure of MLH and survival curves at stressful temperature could be a good criteria combination to identify the improved survival potential of mussels stocks.

The growth response of diploid (2n) and thermally-induced triploid (3n) coho salmon to injected recombinant porcine somatotropin was examined over a 10 week period. All treatments were under-taken using replicate groups of 25 animals per group. Control 2n and 3n replicate groups grew at identical rates throughout the period of study, although 3n fish exhibited lower condition factors. Recombinant poreine somatotropin treated 2n and 3n fish responded positively to therapy and, by week 4 of the trial, expressed significantly greater increases in both weight and length (p < 0.01) when compared to controls. At the end of the study period, soinatotropin treated animals had gained approximately twice the amount of weight of controls. Food conversion efficiencies were greater in treated salmon, regardless of ploidy state. This relationship also extended to weight and length specific growth rates. The economic benefits of commercial application of recombinant porcine somatotropin therapy to triploid Pacific salmon culture are discussed.

Fishing pressure on reef fish stocks, in relation to exploitable biomass, is a useful parameter for fishery resource management but difficult to assess in subsistence fisheries. A methodology for indirect fishery output assessment in island environments is proposed based on estimates of consumption and the relevant seafood trade. Ouvea atoll in the South Pacific (Loyalty Islands, New Caledonia), where subsistence fishing is the main activity, was used as the experimental site. A consumer survey of the islands' households was conducted in June 2000. The sampling plan was determined on the basis of data already available on the population concerned, making it possible to give quantitative and qualitative information on catches. Total catch is estimated to be 212 t y−1 composed mainly of Lethrinidae, Serranidae and Gerreidae. Subsistence activity is the main source of supply for two-thirds of households. These results were validated by a survey carried out on fishers at the same time that confirms the reliability of fish consumption as an indicator of reef fish catches. This study also showed that shoreline fishing remains the main activity in Ouvea: it's practised by 71% of households and provides almost 48% of total landings. A second stage was the identification of variables liable to influence consumption patterns: fishing practice (frequency and gear type), income, and household size seemed to be the main determining factors. These variables were integrated into a multi-dimensional analysis in order to define types of consumers. This consumption-based approach underlies a sampling strategy that could be extrapolated to other small South Pacific islands. It involves advantages of various kinds – accuracy, reliability, and cost-effective implementation – that make it a powerful tool for monitoring island fishery development.

Four experiments were performed with carp (Cyprinus carpio) in ponds of 200 m2 to test the effects of lysine supplementation of feeds with a low protein content. The initial mean weight of the carp and their daily rations were equal in all the ponds of the same experiment. In experiments 1 (400 fish/pond, 3 replicates) and 2 (200 fish/pond, 4 replicates), three diets were tested: A. 30% crude protein (1.7% total lysine); B. 25% crude protein + 0.5% lysine-HC1(1.7% lysine); C. 25% crude protein (1.3% lysine). In both experiments diet B resulted in weight gains equal to diet A, 20% higher protein retention and 20% less nitrogen discharge per kilogramme gain. Diet C lagged 10% in gain and excreted 10% more nitrogen than B. In experiments 3 and 4 (200 fish/pond, 4 replicates) the feed protein was reduced further and 5 diets were tested: A, B, C, similar to the former experiments, D. 20% crude protein + 1.0% lysine-HC1 (1.8% total lysine), E. 20% crude protein + 0.5% lysine-HC1 (1.4% lysine). In both experiments the results of groups A, B and C were parallel to experiments 1 and 2. Diets D and E resulted in lower growth compared to diet C (significantly in experiment 4) and increased body fat content. In conclusion, 30% protein in carp feeds, of which half the protein was soybean protein, could be decreased to 25%, by replacing soybean meal by grains, and supplementing lysine and methionine to the level of the 30% control. Growth was not impaired and nitrogen discharge into the environment was reduced approximately by 20%. Further feed protein reduction to 20%, with lysine supplementation, impaired growth rate below that of the unsupplemented 25% control diet, although total N-excretion was reduced even more.

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce sterility, triploidy induction was attempted by subjecting fertilised eggs to heat shocks. Different combinations of temperature (28, 30, 34, 35 and 36 °C), duration (2, 5, 10 and 25 min) and time of shock initiation (TI = 3, 5 and 7 min post-fertilisation) were tested. Flow cytometry analysis was used to assess ploidy level of control and heat-shocked larvae. Low intensity (28–30 °C) and long duration (10 and 25 min) shocks lead to significantly higher survival (44 ± 26%) and triploidisation (71 ± 26%) rates than high intensity (34–36 °C) and short duration (2 and 5 min) shocks (17 ± 19% and 21 ± 26%, respectively). The most effective conditions for efficient triploidy induction were low intensity shock of 30 °C, applied 5 min post-fertilisation for 25 min. This treatment led to the production of all-triploid populations (100%) with up to 43% survival rate.

In the late 1980's juvenile oysters, Crassostrea virginica, spawned and cultured in New England and New York, began experiencing up to nearly 100% mortalities in some batches of juveniles. The cause of these mortalities was not ascertained immediately, but examination of dead and dying oysters did not reveal a previously recognized disease syndrome. Early studies showed that it was not an environmental or genetic problem, thus we hypothesized that a new, transmissible disease agent caused the observed mortality. This was verified under laboratory conditions where the disease was readily transmissible. Transmission was enhanced by warm water temperatures, 22–26 °C, and salinities of 18–30 ppt. Also, the infectious agent was filterable and sensitive to erythromycin, supporting the hypothesis that the causative agent may be a protistan parasite in the 2–6 μm size range. No evidence to support a viral or bacterial etiology was found.