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 impact of an alien species is correlated with its abundance and potential to colonisenew environments. Consequently, the crucial aspects that give a mytilid species invasivepotential include its strength and capacity for adhesion to a wide variety of substratesand its ecological tolerance to environmental conditions. The alien black pygmy musselXenostrobus securis settles together with the indigenous and raftcultured mussel Mytilus galloprovincialis on hard substrates of the innercoastline of the Ría de Vigo (Atlantic Coast NW Spain). Key parameters for the ecologicalsuccess of these species could include their byssus structure and ecological plasticity.In this study, we assessed their comparative ability to attach to different substratesunder different environmental conditions, using both in situ and laboratory approaches.Byssus threads secreted by X. securis were found to be extremely thin andtheir thickness did not vary with mussel size. This thinness of byssus filaments inX. securis was compensated by the secretion of a huge number (up tothousand of byssus filaments). Although no increase in attachment strength was found withincreasing mussel size in this species, multiple byssus thread secretion might be a keyfactor in the successful invasion of inner areas of the estuary. Furthermore, X.securis exposes a much lower shell area to lift and drag forces in musselconglomerates. By contrast, the indigenous species M. galloprovincialissecretes thicker byssus threads, which provide stronger in situ attachmentdisplaying a linear increase in strength relative to the size of mussels. The exposure ofboth mytilid species to different abiotic factors in the laboratory confirmed the weakerbyssus secretion and limited variation in attachment strength in the alien species. On onehand, X. securis seemed to be better adapted to life on soft bottoms andnot capable of much plasticity when attached to different substrates. However, X.securis might be also well adapted to variable environmental conditions, e.g.,salinity fluctuations, with no need to modify its byssus properties to ensure secureattachment. Attachment strength of M. galloprovincialis was higher thanX. securis in all abiotic conditions tested. Results are discussed inrelation to the ecological tolerance and impact of these mytilid species.

A total of ten Heptranchias perlo, eight Deania histricosa, two D. calcea, and two D. profundorum from the Great Meteor Bank, central East Atlantic, were studied for cestodes. The elasmobranchs were caught using bottom trawl or long-lines during September 1998 in 298–1075 m water depth. Seven different cestode species were found: Tentacularia coryphaenae, Deanicola minor, D. protentus, Grillotia meteori sp. nov., Grillotia cf. microthrix (Trypanorhyncha), Crossobothrium dohrnii, and Crossobothrium sp. (Tetraphyllidea). T. coryphaenae occurred encapsulated in the stomach wall and all other species were found within the host intestine. G. meteori sp. nov. and G. cf. microthrix additionally infested the musculature as well as the stomach and intestinal wall. D. profundorum harboured five different cestode species and D. histricosa, H. perlo, and D. calcea were infested with four, three and two species, respectively. With 332 and 181 specimens, D. minor and G. cf. microthrix were the most abundant cestodes. Grillotia meteori sp. nov., Crossobothrium sp., and C. dohrnii were host specific for Deania profundorum, D. histricosa and H. perlo, respectively. The other species were found in more than one elasmobranch, with Deanicola minor and D. protentus restricted to Deania sp. Most parasites are recorded for the first time from the central East Atlantic around the Great Meteor Bank.

Oil spills are an important source of PAHs in marine and coastal areas and comprise a short- and long-term threat for aquatic organisms. Some PAHs are known to be toxic, in particular mutagenic and/or carcinogenic, and their toxicological effects must be evaluated. Here, the impact of the “Erika” oil spill, which occurred at the end of 1999, was studied by combining chemical (PAH analyses) and toxicological approaches (biological effect assessment). “Erika” elutriates have been found to be more toxic than the elutriate obtained with a crude oil, Bal 250, inducing deleterious effects in Mytilus galloprovincialis and Crassostrea gigas embryos and in Isochrysis galbana algae. The embryotoxicity test in mussel is more sensitive than growth test in I. galbana. Naphthalenic compounds make up more than 95% of total PAHs quantified in elutriates. “Erika” elutriates are enriched with naphthalene, methyl-naphthalene, anthracene and higher-molecular-weight compounds. On the contrary, Bal 250 elutriate is characterized by the highest dibenzothiophene, methyl-dibenzothiophene and dimethyl-dibenzothiophene levels. Weathering does not highly affect the toxicity of the “Erika” oil. This study also confirms the potential impact of the “Erika” fuel on the biological quality of sea water and sediments from Traict du Croisic on the Atlantic coast of France.

Sperm characteristics of scallops have not been well described in the scientificliterature. The effects of sperm release technique (thermal shock versus serotonininjection), of sperm collection technique (testis sampling versus serotonin injection), ofsperm sampling location along the genital tract, of in vitro sperm maturation, and of timepost activation on scallop sperm characteristics were assessed in the present work.Whatever sperm release technique used, no significant differences were observed regardingthe percentage of motile spermatozoa and the velocity of the average path (VAP). Comparedto testicular sperm, a higher percentage of motile spermatozoa, VAP and intracellularadenosine triphosphate (ATP) content were observed for sperm shed after serotonininjection. From the distal part of testes up to the gonopore, an increase of thepercentage of motile spermatozoa and VAP was assessed, suggesting a sperm ‘maturationprocess’ along the genital ducts. A higher increase in the percentage of motile sperm wasrecorded during a 5 min incubation of testicular sperm in seawater containing 2 mMserotonin and seawater containing 10 mM caffein compared to seawater (control). Inaddition, a higher VAP was assessed, incubating testicular sperm in caffein, compared tocontrol or serotonin. Then, the percentage of motile spermatozoa, VAP and intracellularATP content exhibited a progressive reduction during the 10 h swimming period. Mean valuesof the percentage of motile spermatozoa, VAP, sperm track linearity (LIN) andintracellular ATP content recorded at the beginning of the movement period for spermsamples collected after intragonadal serotonin injection, were 82 ± 7%,162 ± 15μm s-1, 0.33 ± 0.12 and 212 ± 133 nmol × 10-9 spermatozoa (n = 9 males), respectively. The presentstudy confirms the existence of a sperm “maturation process” along scallop genital ducts.In addition, the cessation of scallop sperm movement can be explained by the exhaustion ofATP content at the end of the movement phase.

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.

Lagoon fish in New Caledonia are mainly caught by artisanal fisheries and subsistence fishing. Reef fish are the major component of this catch. The present study aimed at estimating these reef fish standing stocks and at finding the main factors influencing the distribution of these fish. Sampling of 904 stations was stratified according to three zones (north, east and west) and three reef types (barrier, intermediate and fringing). Fish communities exhibited bold heterogeneity in their distribution, showing higher biomass (maximum of 447 g·m–2) and total standing stock (43000 tonnes) in the north zone than in the east and west zones. Similarly, observed patterns were dependent on reef types: higher biomass and total standing stock being observed on barrier reefs than on intermediate or fringing reefs. The total standing stocks, which were about 65000 t, were mainly composed of herbivorous fish families such as the Acanthuridae and Scaridae. The differences in the patterns of distribution of species, individuals and standing stocks between reef types may be explained by variations in terrestrial influences and reef morphology, whereas differences among zones were most likely due to accessibility of fishing areas and fishing pressure. The latter is almost non-existent in the north zone, which can thus be considered to be almost unexploited commercially. This most likely explains the high proportion, 77 %, of long-lived species in the biomass of this zone. The results might have implications in management of reefs elsewhere in the South Pacific, for which similar data are only scarcely available.

A number of analytical tools were applied to estimate fish species richness in a small tropical stream (Brazil) that had been sampled by conventional methods (double stick net, electrofishing) and rotenone. Three sites were compared in two seasons each and a total of 34 species were captured. The sampling efficiency of electrofishing was much better than that of the double stick net and little worse than of rotenone. No estimator was thoroughly consistent and accurate in predicting species richness on the basis of electrofishing, but the Homogenous Model, which assumes that all species have the same detection probabilities, was best. The rarefaction technique should be used with caution as it may produce misleading results in species richness predictions.

Les Siluroidei sont connus pour avoir, en milieu naturel, une activité trophique essentiellement nocturne. Ceci a été confirmé au cours d'expériences réalisées en conditions d'accès constant à une source de nourriture, ou encore à l'aide de distributeurs d'aliments à la demande. Cependant, en conditions limitantes en température ou en oxygène, l'activité trophique de certains Siluroidei devient dépendante de ces deux facteurs, et n'est plus synchronisée par l'alternance jour/nuit. Le rythme nycthéméral d'activité trophique des espèces étudiées présenterait donc une acrophase préférentiellement nocturne, mais posséderait une certaine plasticité. L'existence d'un contrôle d'origine endogène de ce rythme est aussi discuté. Rares sont les poissons Siluroidei qui refusent de s'alimenter lors de distributions diurnes d'aliments. Il convient d'évaluer les conséquences que pourraient avoir sur la croissance des horaires d'alimentation non synchrones avec les rythmes alimentaires. L'effet de l'heure des repas sur les performances de croissance montrent une tendance générale à une croissance supérieure chez les animaux nourris de nuit par rapport aux animaux nourris de jour. Cependant, le mode de distribution choisi (en repas ou en continu) semble avoir plus d'influence que l'heure de distribution sur les performances de croissance. Certains auteurs ont aussi montré une augmentation de l'adiposité des poissons lorsqu'ils n'étaient pas nourris en phase avec leur rythme alimentaire.

The catch from bottom longline stations sampled from a series of research cruises around Lanzarote and Fuerteventura (Canary Islands, NE Atlantic) was analysed in terms of fish distribution, density and diversity. The distribution of the number of species and individuals caught per station appeared to fit well the Poisson and Exponential distribution function, respectively. In particular, the parameter of the Poisson’s distribution appeared to provide an index of the point (at station scale) diversity, and its confidence interval, allowing for statistical comparisons. The relationships between point diversity, the alpha diversity (in the depth strata) and the beta diversity (along the depth gradient) were investigated. Around the islands, the density and the point diversity of the predator fish declined with depth down to about 800 m and then increased in the deeper stratum. The alpha diversity was the lowest in the deeper stratum but the taxonomic distinctness was similar to that of shallower strata. The beta diversity showed some faunal breaks along the depth gradient. The carnivorous fish fauna can be understood as comprised of three major assemblages: shelf, upper slope and mid-slope that are different both in terms of species composition and point, alpha and beta diversities. The relevance of this simple method for ecological studies of fish assemblage in the context of non-trawlable grounds is discussed, in particular for the slope and other areas of established or developing deep-water fisheries.

From April 2003 to April 2004 monthly sea surveys were conducted around 2 fish aggregating devices (FADs) moored at 2000 and 2500 m depth in Martinique (Lesser Antilles). The use of a dual frequency splitbeam echosounder combined with an underwater camera and fishing methods allowed assessment of average space and time distribution of pelagic fish aggregated beneath the FADs, as well as identification of their overall size and species composition. At daytime, 4 fish aggregations were identified at each FAD, representing 4 distinct types: i) an aggregation of small juvenile tuna (mean fork length, FL: 30 cm) observed very close to the surface in 25% of daytime periods; ii) a small surface aggregation dominated by carangids, Caranx crysos, present in 65% of daytime periods; iii) a large sub-surface aggregation observed during all daytime periods: this aggregation appeared to be primarily comprised of 58 cm FL blackfin tuna (Thunnus atlanticus), mixed with yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas of the same size; and iv) sub-surface scattered large predators (mainly blue marlin, Makaira nigricans) present in 10% of daytime periods. A smaller sub-surface aggregation comprised of medium tuna mixed with “extranatants” (fishes which remain within 10 to 50 m of a FAD) was observed in 75% of night-time periods, whereas unidentified scattered fishes were detected from 70 to 400 m depth. The low daytime vulnerability of medium sub-surface tunas to applied line techniques leads us to assume that their feeding motivation was low during daytime. These tunas could preferentially feed on mesopelagic organisms during night-time and transition periods around Martinican moored FADs. Local fishermen mainly targeted the large scattered predators using very small tunas as living bait. The sub-surface tuna aggregation hence appeared to be currently unexploited by local fisheries, though it represented the large majority of the pelagic biomass around the moored FADs.

Deepwater fish are characterized by long lifespans, late maturity and low productivity. This implies slow recovery from low biomass levels and it is, therefore, important to manage these stocks correctly to avoid overfishing. However, these stocks are generally data poor, which it makes difficult to apply quantitative assessment models on which to base their management. The management strategy evaluation (MSE) approach consists in evaluating the performance of management strategies by simulation before their implementation. In the evaluation, the main sources of uncertainty in a fishery system and its management process should be taken into account in order to find robust management strategies. Thus, the MSE approach is relevant to the management of data-poor stocks. We used the FLBEIA software, an FLR library coded in the R statistical language, to conduct a bio-economic impact assessment of fisheries management strategies. We evaluated the performance of several management strategies in three different deepwater case studies using the MSE approach: beaked redfish (Sebastes mentella) in the Norwegian Sea, blackspot seabream (Pagellus bogaraveo) in the Strait of Gibraltar, and French mixed deepwater fisheries in the North East Atlantic. In conclusion, we found that the S. mentella stock is very sensitive to the stock recruitment relationship chosen. For P. bogaraveo, simulations showed that the present constant catch management is as good as more sophisticated strategies. Finally, in mixed fisheries, case study fleet dynamics were key for the success of management strategies

Brown trout and rainbow trout (average weight 100 g) were reared in fresh water at 12 °C under the same conditions before transfer of brown trout to sea water, in order to compare nitrogen utilisation in the two species. Apparent protein digestibility (ADC), nitrogen (ammonia and urea) excretion, protein productive value (PPV) and actual observed nitrogen mass balance were determined. Rainbow trout raised in fresh water had a higher growth rate (1.1 vs 0.8%.d−1), better food conversion ratio (0.7 vs 1.0), better ADC (91 vs 85%) and PPV (45 vs 35%) and lower ammonia excretion rates than brown trout reared in fresh water. Transferring brown trout to sea water induced lower PPV (30%) and ammonia and urea excretion. Salinity did not modify metabolic efficiency in brown trout. Fat content was higher in brown trout (7.7-8.9% ww) than in rainbow trout (5.7-7.6% ww). Nitrogen mass balance indicated that compounds other than ammonia and urea were produced in higher quantities by seawater brown trout. Behaviour, less domestication and specific ability to utilise protein could explain the differences between the two species.

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.

In recent years, with increased effort to bypass and guide fragile stocks of juvenile salmon in the Columbia Basin past hydroelectric projects, it has been increasingly important to obtain fine-scale fish behavior data in a non-intrusive manner. The Dual-Head Multibeam Sonar is an emerging technology for fisheries applications that addresses that requirement. It has two principal advantages over traditional hydroacoustic techniques: 1) it allows for simultaneous large-volume coverage of a region of interest, and 2) it affords three-dimensional tracking capability. The use of Dual-Head Multibeam Sonar in this study resulted in an unprecedented insight into fine-scale smolt behavior upstream of a prototype surface collector at the Bonneville Dam first powerhouse in 1998. Our results indicated that outmigrant juvenile salmon had an increased likelihood of milling or holding. This discovery will lead to better design criteria for future bypass and collector systems. Future fisheries multibeam sonar systems will likely be fully integrated systems with built-in real-time tracking capability. These systems may be used to track targets relative to physical guidance structures or other behavior-modifying stimuli such as light, turbulent flow, electrical/magnetic fields, or low-frequency sound and vibration. The combination of fine-scale fish behavior data and environmental parameters will yield better design criteria for the safe passage of listed or endangered species of Pacific salmon.

In mainland Portugal, rays constitute an important by-catch of multi-gear shelf fisheries. However and despite their economical importance, landing information discriminated by species is scarce. The relative stability in Portuguese annual landings of rays and skates can be misinterpreted as no evidence for species declines. The present concern on the overexploitation of individual species arises from both theoretical considerations about biological and ecological traits and for historical reasons.

This work constitutes an approach for a retrospective analysis of ray landings in mainland Portugal. Data from research surveys carried along the Portuguese coast was used to infer possible changes in species composition on Portuguese landings. Clusters were determined based on data collected during surveys from species composition for three time-periods, 1989-1991, 1995-1997 and 2001-2003. The relative importance of the associate species within clusters was the input data to define discriminating rules posteriorly used to assign clusters to landings from each commercial vessel. The results show an increase of species relative importance and changes on species abundance: Raja brachyura and Raja clavata decreased, whilst Leucoraja naevus, increased. Furthermore, it was observed a decrease on the mean weight of the two first species and a relative stability in the last one. Such results reflect the importance of specieslife-history characteristics in particular, on the response to fishing impact.

The present study analyses the spatial and temporal distribution of the pelagic stingray (Pteroplatytrygon violacea) in the south-western Atlantic Ocean, based on data collected between April 1998 and March 2006 by the National Observers Program of the Uruguayan Tuna Fleet. During this period, data were recorded on 51 commercial fishing trips, in which a total of 2 306 851 hooks were set and 2740 stingrays captured. Of these, the sex was determined for 1329 individuals and the size for 944. The average disc width was 47 ± 8 cm (range: 24–82 cm) for females and 44 ± 5 cm (range: 28–84 cm) for males. The results indicate that the species seems to prefer warm temperate and tropical waters. There were no capture records in waters at <15.3 °C. The data collected suggest a mating season in late spring with a gestation period of 2 to 4 months and births occurring during late summer and early autumn. The increasing bycatch of this ovoviviparous species in pelagic longline fisheries, with an unknown survival rate after discard, coupled to its low reproductive potential, call for better monitoring in order to accurately determine its current conservation status.