European hake Merluccius merluccius is the main commercial demersal species in the Gulf of Lions (Northwestern mediterranean). This fish is exploited by French and Spanish trawler fleets and by small-scale fisheries using gillnets and longlines. Data on landings and the demography of catches by type of gear are now available for the period 1988–1991. The assessment of the hake stock was carried out using methods of virtual population analysis (VPA), or cohort analysis, based respectively on mean pseudocohorts and cohorts by age. The results of these VPA were then analysed and compared from a methodological point of view. The general results have confirmed previous studies with regard to the level of exploitation of the species. The two methods gave quite similar results for fishing mortality rates and for mean biomass. The maximal fishing mortality rate was observed at age 4, but it was already high at age 1, due to the exploitation of juveniles by trawlers. The mean biomass was about 7 000 tons. The high values for turnover (about 80% or more) and for the maximal biomass/mean biomass ratio (23% or more) indicated a high level of exploitation but did not seem high enough to be dangerous for the stock. Yield-per-recruit analysisshowed also that the present level of exploitation is far above the optimal sustainable level.

The Pacific herring Clupea pallasi population in Prince William Sound (PWS), Alaska, is both a valuable commercial resource and an important forage species for marine fish and wildlife. Historically, the herring were managed by a combination of age-structured models and egg deposition estimates. When these methods predicted a large return for spring 1993 that failed to materialize, we began surveying with echointegration–purse seine methods. After a decade of acoustic surveys, we show the new approach yields highly precise biomass estimates, which are consistent with historical measures of the miles of beach spawning. When compared, we show the traditional methods overestimated stock biomass, which resulted in harvest rates approaching 40%. In contrast, the acoustic methods are most likely to underestimate biomass. Since the acoustic estimates can be quickly obtained, we recommend their use to set harvest quotas for the fishery in the spring just prior to harvest. The shift from the traditional preseason to inseason management practices for herring in PWS is consistent with the Precautionary Principle by the fact that protection of the spawning population does not rely on the ability of science to predict how the population is changing. Furthermore, synoptic infrared measurements on our night-time acoustic surveys revealed herring to be the most important winter forage to marine birds and wildlife in PWS, including the endangered Steller sea lion Eumetopias jubatus. Given the importance of forage to marine birds and wildlife in the North Pacific during the extended winter conditions (October–March), the implementation of inseason management for herring using echointegration–purse seine techniques may be the most effective method to restore depressed populations of marine birds and mammals in the North Pacific.

Survival and growth performances of autotriploids in rainbow trout (Salmo gairdneri) and three types of triploid hybrids between female rainbow trout and brown trout males (Salmo trutta,) coho salmon males (Oncorhynchus kisutch) and brook trout males (Salvelinus fontinalis) were analysed relatively to the parental species in freshwater farming conditions. At the end of the immature period, autotriploids exhibit moderate but significant depression relative to the control for both survival (about 25% depression) and growth (10 to 15% depression). Most of this depression is established during the first three months of life, triploids appearing very similar to the control later on. At the onset of sexual maturation at 2 years old, relative value of triploids becomes higher than that of the control, for both survival and growth. Long term evaluation (2+ or 3+) balances in favor of triploids with particular advantage for triploid females. Triploid hybrids exhibit much more important depression in early survival (up to 60%). Later on, their survival remains always lower than those of parental controls. Their growth performances are intermediate between their two parental species. Despite a relative advantage for these groups during the onset of sexual maturation in control groups, especially for growth, long tem evaluation is in favor of diploid rainbow trout, but in some specific cases.

Day and night acoustic surveys were used to compare fish stock estimates at eight European reservoirs and one flooded mining pit. During both photoperiods of summer, higher fish biomass was observed in the uppermost 4 m of the water column by horizontal beaming than in deeper water by vertical beaming. Comparisons of volume backscattering coefficient (sv), fish biomass (kg ha−1), abundance (ind. ha−1) and average fish weight (g) did not show a common pattern among the reservoirs but were found to vary significantly across photoperiods. At most reservoirs, the night surveys had higher estimates than day surveys. However, at several reservoirs the opposite pattern was observed. These patterns could not be explained by the species composition of the fish stocks. Fish size distributions were found to be different between day and night. A higher proportion of 1+ and older fish were found during the night at two of three studied waterbodies. In general, it was not possible to decide whether day or night acoustic surveys gave more reliable fish stock assessments. We advise performing both day and night transects on a given water body before deciding when to conduct the full survey. For a complete fish assessment it is very desirable to combine acoustic mobile surveys with active sampling gear.

This review presents environmental and biological indicators of the impact of three major categories of inputs in coral reef lagoons i.e. particles, nutrients and metals. Information was synthesized to extract well established indicators together with some interesting new concepts currently under development, and to provide the reader with an assessment of their respective advantages and drawbacks. The paper has been organized according to the capacity of three categories of indicators to respond either in a specific or a non specific way to a given source of input. The first section focuses on abiotic indicators which main interest is to respond instantaneously and in a truly specific way to a given source of input. The second and third sections present informations on bioindicators either at the sub-individual level or at the individual to community level, indicator specificity generally decreasing as a direct function of biological or ecological complexity. This review showed that even though significant work has already been done on coral reef ecosystems, much more scientific studies are still needed to answer the growing local demands for simple and truly validated tools to be used in environmental surveys. It is further stressed that, due to the biological and environmental diversity of coral reef lagoons, a preliminary step of on-site validation must be considered as an absolute prerequisite when indicators are planned to be used in the frame of a local environmental monitoring programme.

Otolith shape analyses were conducted on three different species of Mullidae (Mullus barbatus barbatus, M. b. ponticus and M. surmuletus). The otolith shape was described by 19 harmonics from elliptic Fourier descriptors. In a first step, their comparison through canonical discriminant analyses (CDA) was run for all fish with right otoliths, left otoliths and both otoliths pooled. The latter possibility had a higher discriminating power and allowed much more visually explicit results. This implied that the two otoliths were not similar as often claimed, and had each their specific information. In a second step, the CDA demonstrated strong spatial discrimination of local populations from various areas within the Mediterranean basin, i.e. NW Mediterranean, Aegean Sea and Black Sea, and between sites within each area. The percentage of well classified individuals of M. barbatus in predefined groups varied between 78 to 100% depending on sites, and even reached 100% for each site for M. surmuletus. These spatial patterns were most likely linked to differences in environmental conditions between areas and sites, such as effects of strong river runoffs and differences in depths and/or habitat types. In a third step, CDA also evidenced ontogenetic discriminations of mullet populations that could be linked (i) to influence of diet of fish of various sizes and (ii) to changes in physiological conditions according to the stage of development of the fish.

The recruitment of Strangomera bentincki (common sardine) and Engraulis ringens (anchovy) and the relationships with oceanographic conditions in the upwelling ecosystem of central-south Chile were investigated from 1990 to 1998, with emphasis on the 1997–1998 El Niño. Time series of recruitment, biomass, local sea surface temperature, and a coastal upwelling index were used to explore relationships during the spawning (July–August) and pre-recruitment (August–December) periods. The 1997–1998 El Niño caused physical changes in the small pelagic fish habitat off central-south Chile. Anomalous sea surface temperatures (SST) and upwelling indexes began to be detected from May 1997 and persisted into 1998. Recruitment of common sardine showed significantly negative relationship with SST anomalies during the pre-recruitment period, as well as with the upwelling index during the peak of spawning. However, the recruitment of anchovy did not seem to be affected by the environmental changes observed in the 1990s. Instead, the recruitment rate of anchovy showed negative relationship with the recruitment rate of common sardine. We conclude that the conditions of the 1997–1998 El Niño off central-south Chile affected the survival of common sardine offspring, and that the recruitment success of anchovy could be determined by less-abundant cohorts of common sardine through a biological mechanism of interaction.

In this paper, we present an approach to compare the impact of different management options on the dynamics of a mixed fishery. We used ISIS-Fish, a simulation tool aimed at evaluating the impact of spatial and seasonal management measures on the dynamics of mixed fisheries. The French Nephrops norvegicus (Norway lobster) – Merluccius merluccius (hake) mixed fishery of the Bay of Biscay was chosen as a study case. First, we parameterised the population and exploitation models. We then selected several management measures, including marine protected areas (MPAs) and total allowable catches (TAC), and parameterised fishermen's reaction to each measure. Then, a sensitivity analysis was performed according to a fractional factorial experimental design. Management scenarios were assessed and compared using a statistical simulation design. The sensitivity analysis showed the large influence of some parameters, such as natural mortality, N. norvegicus fecundity, and catchability on both abundance and catches. Given model parameters, an improvement of trawl selectivity and several MPA designs (differing in size, seasonality and location) were found to result in a significant increase in abundance over 10 years, especially for N. norvegicus. This study illustrates the need for a pluri-specific approach to fisheries assessment and management.

The pole and line tuna fishery in the Maldives relies heavily on an array of 45 anchored fish aggregating devices (FADs), making it one of the largest anchored FAD-based tuna fisheries in the world. We examined the behaviour of skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tuna around anchored FADs (1 000 to 2 000 m deep) in the Maldives using passive acoustic telemetry. Eight neighbouring FADs (distance range: 30 to 95 km, average: 50 km) were equipped with automated acoustic receivers in January 2009, for a period of 13 months. A total of 40 skipjack (37−54 cm FL) and 21 yellowfin (35−53 cm FL) tuna were tagged with Vemco V13 transmitters in January (start of the northeast monsoon, dry season) and November (end of the southwest monsoon, wet season) 2009 and released at the two central FADs within this instrumented array. No movement between FADs was observed for any acoustically-tagged tuna in the instrumented FAD array. These results suggest that FADs in the Maldives may act independently. The maximum time a tagged skipjack remained associated with a FAD was 12.8 days in January but only one day in November. In addition, residence times at FADs were found to differ with time (month) and space (FAD location) for skipjack tuna, suggesting that external biotic factors (e.g., prey, conspecifics or predators) might influence the time this species spends at FADs. In November, the residence times of yellowfin tuna (maximum observed time: 2.8 days) were three times greater than those of skipjack tuna at the same FADs. This specific difference could be explained either by the two species responding to different factors or by the species’ responses being dependent on the same factor but with different thresholds. No particular preference for time of departure from the FADs was observed. Some monospecific and multispecific pairs of acoustically-tagged individuals were observed leaving the FADs simultaneously. Thus, this study indicates a high degree of complexity in the behavioural processes driving FAD associations.

Few studies have compared the suitability of different artificial reef construction materials in terms of their efficacy in acquiring diverse faunal assemblages. We compared the fishes associated with 12 co-located reefs constructed of limestone quarry boulders, concrete-gravel aggregate, or concrete-tire aggregate (four of each substrate) in 7 m of water, 200 m offshore Miami Beach, Florida, USA. All 12 reefs were deployed 100 m apart the same day in two lines of six. The four quarry stone reefs consist of a pile of 50 boulders each. The remaining eight reefs, of concrete-gravel aggregate and concrete-tire aggregate, were each constructed with 25 1.5 m edge and 25 1.2 m edge tetrahedron modules. Every two months from October 1998 to February 2001, SCUBA divers recorded fish species, abundance, and length, as well as spiny lobster, Panulirus argus, abundance. One hundred and forty-six species of fishes were recorded during the study period. The abundance and species richness of fish on each treatment exhibited a significant (p<0.05) seasonal variation with summer months having the greatest numbers and winter the lowest. There was no significant difference in total fish or spiny lobster abundance or fish biomass amongst the three reef types (p>0.05). Likewise, multi-dimensional scaling of Bray-Curtis dissimilarity indices did not indicate clustering of fish assemblages by reef type. Comparison of pre-deployment fish counts from the reef sites and neighboring hard bottom and jetty with counts from the same sites two years post-deployment indicate the artificial reefs increased both fish abundance and richness in the local area.

Within the distributional range of a species the number of self-sustaining populations can vary, from one population for panmictic species such as American eel to many populations as observed in Atlantic salmon. This "species-level" characteristic is defined here as "population richness". Aspects of geographic patterns in population richness in the northern Atlantic for Atlantic salmon, American shad, rainbow smelt, Atlantic herring, Atlantic cod, haddock, winter flounder, yellowtail flounder, Atlantic mackerel, and European eel are described. It is concluded that events at the early life-history stages, involving "retention" of the eggs and larvae in relation to particular physical oceanographic features, are involved in the definition of population richness.

Thirty French fleets fishing primarily in the Bay of Biscay were defined based on techno-economic input criteria: i) 18 fishing gear or gear combinations ii) the location of fishing grounds visited during a year (<12 nautical miles from coast, beyond 12 nm or both) and iii) total vessel length (<20 m for trawlers and other gears <24 m). The fleets were then characterised in terms of horse power, economic dependence on a list of nine dominant commercial species (sole, Nephrops, sea bass, hake, monkfish, anchovy, cuttlefish, sardine and squid) and their contribution to the landings of these species from the Bay of Biscay. Most fleets derived the majority of their income from one or two among the nine species. Species dependencies changed little during the study period, except for those vessels targeting anchovy before the fishery restrictions starting in 2005. Fish community impacts were compared based on fleet landings' profiles. Twelve landings profiles were determined using hierarchical cluster analysis. Fleets using similar gears had the same landings' profiles and therefore exercised similar pressures on the ecosystem, though not always in the same areas. The depletion of anchovy and the closure of the fishery lead to a change in landings profile for offshore pelagic trawlers from anchovy dominance to one with a larger proportion of albacore and sea bass. During the study period, the overall vessel number decreased from 2163 to 1845. Few vessels changed fleets, but if they did, they primarily started to fish closer to the coast, which might be a result of increasing fuel prices.

Automated acoustic receivers are now widely used by biologists to study the behavior of fish. However, currently available acoustic receivers require physical recovery of the units to download stored data. Such operation is often difficult in remote study areas like in the open ocean. We present a new satellite-linked acoustic receiver (Vemco VR3-Argos) that allows downloading data through a satellite uplink (Argos). The VR3-Argos can last up to one year, sending GPS positions and tag data at regular time intervals. We illustrate the advantages of this new technology with tagging data from 121 fish of seven species (yellowfin tuna, bigeye tuna, skipjack tuna, wahoo, dolphinfish, silky shark and oceanic triggerfish) caught and released around drifting fish aggregating devices (FADs) in the Western Indian Ocean, far from any land. In opposition with the classic acoustic receivers (Vemco VR2), the use of VR3-Argos allowed to collect data for several weeks after leaving the drifting FADs. Maximum residence times of 3 days for bigeye tuna, 7 days for skipjack, 8 days for wahoo, 10 days for silky shark and 15 days for yellowfin tuna, dolphinfish and oceanic triggerfish could be recorded. VR2 and VR3-Argos are equivalent in terms of quality of residence times data, however depth data obtained through satellites are aggregated in 8 classes for compression purposes, which leads to a loss of precision available with raw data. Future directions of this technology are discussed.

For last 20 years, the fish communities in the Central Delta of the Niger River have been subjected to: (i) two drought periods in 1973 and 1984, (ii) a dramatic increase of fishing and, (iii) the building of an electric-power dam in 1984. At different levels, these various factors modified the biological cycle of the fish which are adapted to the former hydrological cycles of the Niger and the Bani rivers. The Sahelian drought is responsible for a decrease in both flood duration and of the inundated area of floodplain which varies from 20 000 km2 to 5 000 km2. From 1968 to 1989, fish landings declined from 90 000 metric tons to 45 000 metric tons. During the same period, as fish catches fell, yields per hectare increased from 40 kg in 1968 to 120 kg in 1989. This phenomenon is linked to the decrease of the average age of the fish (69% of fish catches are under one year old) in response to the increased fishing mortality and natural mortality which is higher during the drought period. The increase in fish productivity is characterized by a depletion of species such as Gymnarchus niloticus, Polypterus senegalus, Gnathonemus niger, whose reproduction are linked to the floodplains and of species like Citharinus citharus and Clarotes laticeps which visit frequently flooded areas. Concurrently, families such as the Cichlidae or Clariidae, which are resistant to low oxygen concentration, increase. Species which are under one year old at first reproduction and have several spawning periods per year, are the more abundant in fish communities.

Because preying on close relatives may cause a loss of inclusive fitness, cannibalistic animals are generally deemed to cannibalise non-related conspecifics preferentially to kins. Whether this basic principle also applies to fish exerting intracohort cannibalism at an early developmental stage is uncertain, and more intense cannibalism among mixed progenies might just be a consequence of greater size heterogeneity. To investigate this, progenies of sharptooth catfish of equivalent initial body weights but with contrasting size heterogeneity were reared separately or in mixed groups containing equal proportions of each progeny (27 ± 1°C, 12 h light:12 h night, 2.5 L aquaria, 100 or 200 fish·L–1). Cannibalism was monitored on a daily basis until the end of the larval stage (3–15 days after hatching). Cannibalism in mixed groups was intermediate between those in pure progenies, and was positively correlated (R2 = 0.803, P < 0.01) with initial size heterogeneity, irrespectively of fish origin. This finding does not exclude that catfish larvae were able to discriminate between siblings and non-related fish, but this obviously had very little influence on cannibalism. The implications of this finding are discussed, as they apply to prey selection in fast growing larvae, and aquaculture of catfish.

In October and November 2003 a bloom of the toxic dinoflagellate Alexandrium catenella was observed in the North-east zone of Thau lagoon (French Mediterranean coast). Sea water samples were collected every hours to evaluate time-related variations of phytoplankton concentrations and to compare the relative ratio of A. catenella versus other phytoplankton species during the outbreak. From these observations, trials using recirculated sea water systems were performed to: i) evaluate the physiological effects on oyster of increasing proportions of A. catenella within a mixed microalgal diet where the non-toxic diatom Thalassiosira weissflogii was present at concentration: 1500 cells ml−1, ii) compare the effect of two temperatures (12 °C and 18 °C) on paralytic toxin accumulation rates in oyster flesh by ion-pairing high performance liquid chromatography (IP-HPLC) detection, iii) analyse toxin biotransformation during the contamination process, iv) evaluate the role of the different types of oyster tissue on the bioaccumulation mechanism.

The results showed: i) a significant effect of temperature increase on clearance rate and toxin uptake, ii) no detectable time-related effects of toxic algal food on pre-ingestion sorting or on toxin profiles in oyster flesh, iii) either negative or positive effects of A. catenella concentrations on toxin uptake (“threshold” effect), iv) high amounts of toxins in the digestive gland, accounting for more than 80% of overall shellfish toxicity. The daily amount of toxins (Q tox) taken up by each oyster was evaluated by means of a global one-compartment model. However a two-compartment model finally gave the best match with real contamination kinetics, since it integrated both toxins sequestered in oyster tissues and toxins moving in through the digestive tract.

Two feeding experiments were conducted to evaluate growth and survival rates of African catfish (Heterobranchus longifilis Valenciennes, 1840) larvae fed with different diets: live Artemia nauplii, frozen Artemia nauplii, live zooplankton (Moina micrura), frozen zooplankton (Moina micrura), a dry diet based on yeast powder and beef liver, and a commercial trout starter diet. The larvae were fed in excess, six timesper day every 4 hours, from the onset of exogenous feeding up to an age of 14 days. In both experiments the final mean weight and specific growth rate of fish fed live Artemia nauplii were significantly higher than those of fish fed other diets (p > 0.05). Survival rates of fish fed Artemia (live or frozen), Moina micrura (live or frozen) and dry diet did not significantly differ (p > 0.05) and ranged from 79 to 92% and 61 to73% for experiment 1 and experiment 2, respectively. The commercial trout diet led to significantly lower growth and survival rates in comparison to all other diets tested. Although it led to a lower growth rate than that obtained with Artemia, Moina micrura proved suitable for first feeding of H. longifilis larvae. Locally available in West African waters, this cladocera could constitute a valuable alternative for larval rearing when a shortage of Artemia is expenenced. The results also showed that the artificial feed based on yeastpowder and beef liver leads to survival rates as high as those obtained with living diets and thus represents a promising way for feeding H. longifilis fry. However, further studies on the nutritional requirements of the larvae remain necessary in order to improve the efficiency of dry diet in terms of growth performance.

Escapement through the body or under the footrope of the sampling trawl used for the Mediterranean international trawl survey programme (MEDITS) was assessed i) by means of visual observations performed with a towed operating vehicle equipped with a high-sensitivity video camera, and ii) by attaching small bags to the outside of the trawl body and under the footrope. Due to the small size of most of the individuals present in the study area and to the towing speed, fish behaviour in front of the trawl could not be frequently observed. In contrast, their behaviour was easily observed inside the net, especially upstream and inside the codend. Some species, such as horse mackerel (Trachurus sp.), showed greater swimming endurance compared with others such as annular seabream (Diplodus annularis). In three fishing trips conducted in different seasons in 1996 and 1997 to obtain data on several species in different areas of the Adriatic, six small net bags were mounted outside the body of the MEDITS trawl to quantify escapement through the trawl belly and under the footrope. Significant escapement of many species occurred in the near-bottom part of the side panels. Norway lobster (Nephrops norvegicus) had the highest rate (64 %), mainly represented by small-size individuals. The escapement of greater forkbeard (Phycis blennoides) was also high (53 %). For hake (Merluccius merluccius), common pandora (Pagellus erythrinus) and poor cod (Trisopterus minutus capelanus), rates ranged from 10 to 16 %. The escapement of red mullet (Mullus barbatus) was very low despite their great abundance. Blue whiting (Micromesistius poutassou) escaped mainly through the mid-height part of the side panel. This great variability of escapement values could affect the proportion rates of the species sampled during a standard survey. Different escape behaviours among size classes were observed for M. poutassou, T. minutus capelanus and P. erythrinus, with smaller individuals tending to escape towards the bottom and larger ones towards the higher parts of the trawl body. In the species where the escape rate was size-dependent, therefore, the size-frequency distributions obtained from the codend catch may not reflect actual size-frequency distributions.

A total of 361 skipjack tuna (Katsuwonus pelamis) between 41.5 and 71.5 cm fork length and 333 yellowfin tuna (Thunnus albacares) between 48 and 150 cm fork length were collected in the western Indian ocean, between latitude 5° N to 10° S and longitude 45° to 65° E from February 1989 to November 1990. Yellowfin populations have one major reproductive season during the north monsoon while in skipjack the reproduction is almost continuous all year round with two peaks in activity during north and south monsoons. The gonadosomatic indexes (GSI) are correlated with the three climatic situations: the north monsoon, the south monsoon and two inter-monsoon seasons. The steroid hormone variations (oestradiol, oestrone and testosterone) are well correlated with the GSI in females. In males, maximum levels coincided with the two main reproduction periods in skipjack while the maximum values of testosterone and 11-ketotestosterone levels were only found during the north monsoon. Even if both species are continuous spawners, these results indicate the existence of different reproductive traits, especially when considering steroidogenesis and vitellogenesis. These findings suggest that over our fishing zone, the reproductive activity is significantly modulated by climatic changes.

Eighty-seven two-hour acoustic surveys (radius 0.8 nautical mile, vertical range 0–500 m) around 17 fish aggregating devices (FADs) were conducted in French Polynesia between December 1995 and February 1997. Associated tuna densities were calculated using two different techniques: echo counting when the fish had sufficient distances from each other and echo integration when the fish swam close together (in schools). No acoustic detection of tuna was observed during 27 of the 87 surveys, representing 81 % of all the nocturnal surveys and 15 % of the diurnal ones. The 60 other surveys showed three different classes of aggregations: (1) ‘deep scattered fish’, observed 45 times, (2) ‘intermediate scattered fish’, observed 16 times, and (3) ‘shallow schooling fish’, observed 16 times. Sometimes aggregations of different classes were observed beneath the same FAD. The size of the fish inside the aggregations (determined from target strength values), the distance between the individuals, and the depth of the fish all decreased from ‘deep scattered fish’ to ‘shallow schooling fish’ (100–300 m for ‘deep scattered fish’, 50–150 m for ‘intermediate scattered fish’, and above the depth of 50 m for ‘shallow schooling fish’). Fish densities also varied according to the class of aggregations: 7.3, 26, and 801 fish per km3 on average for ‘deep scattered fish’, ‘intermediate scattered fish’, and ‘shallow schooling fish’, respectively. The highest densities were observed during daytime, while night-time observations indicated a variety of situations, from the absence of individuals to large amounts of fish.