The ability of captive-reared turtles to survive in the wild is not precisely known, nor are movements of immature turtles in the open ocean. To provide information on these issues, a satellite tracking experiment was conducted in the western Indian Ocean to monitor oceanic movements of immature green turtles. Two wild turtles and four captive-reared individuals were tracked. The latter had been displaced after birth from nesting sites to a distant rearing site. Wild turtles survived after release, but did not move far away from release site. We hypothesize that this resident behaviour may be explained by stage-specific habitat requirements. Captive-reared turtles survived after release and migrated over thousands of kilometres. Among these, the oldest immature turtles retrieved the foraging sites of their native population, with movement patterns similar to those displayed by adults. Observed movements may be linked to hydrographic conditions such as general oceanic circulation, sea temperature and thermal fronts.

Seasonal changes in nucleic acid concentrations and amino acid profiles in the muscle of juvenile Aristeus antennatus were investigated. RNA content, RNA:DNA and RNA:protein ratios varied significantly between seasons (p < 0.05), being the lowest and the highest values obtained in winter and spring/summer. A significant variation in the total amino acid content (TAA) from winter to summer was observed (p < 0.05). In fact, during this period a significant percent of increase in total non- (NEAA; 20.2%) and essential amino acids (EAA, 18.7%) contents occurred. Concomitantly, a significant decrease in the free amino acid (FAA) content from winter to summer was observed. A higher percentage of decrease with free essential amino acids (FEAA; 56.6%) in comparison to free non-essential amino acids (FNEAA; 34.2%) was attained. The significant increase in RNA and TAA contents from winter to summer may be related with protein synthesis. On the other hand, the lowest values obtained in winter may be due to a reduction in feeding activity; in this period the muscle protein must be progressively hydrolysed, which is evident with the higher FAA content. The liberated amino acids enter FAA pool and become available for energy production.

The scope of this study is to investigate the extent to which area-based management may have influenced the fishing efficiency of the Danish and Dutch demersal fleets harvesting cod, plaice and sole in the North Sea. Special consideration is given to the ‘plaice box’, a restricted area where fishing is prohibited to towed-gear fleets of horsepower exceeding 300 hp. An index of fishing power is calculated as the log-ratio between the catch per unit effort (CPUE) of any vessel and some survey abundance index. Annual trends in fishing are calculated as the year-effect derived from a general linear model (GLM) analysis of the index of fishing power. The fishing efficiency of Danish gill-netters and, to some extent, Danish seiners, has overall increased inside the ‘plaice box’, whilst remaining relatively stable outside. However, the fishing efficiency of the other exemption fleets has apparently been subject to little change. Overall, it is not possible to determine the extent to which the ‘plaice box’ has contributed to the fishing efficiency dynamics of the exemption fleets. However, some of the results of this study bear out the conclusions from recent investigations.

This paper addresses the question of the relative importance of economic and regulatory (administrative) factors on the profitability of various components of a fishing fleet. The argument is that, while the official purpose of most regulatory measures is resource conservation, these measures may significantly influence the relative levels of incomes generated by various components of the fleet. When a large part of fisheries management is under the control of fishermen themselves, this illustrates how the endogenous generation of rules by groups of users may affect both economic efficiency and equity. The analysis relies on a field survey of a small-scale inshore fishing fleet of the Northwest part of Brittany (France),which provided data for simulations concerning the impact of various factors on the profitability of boats. According to the results of these simulations, two regulations, concerning the cost of access to some resources and the control of fishing effort, play a significant role in the difference of profitability observed according to boat size. At a time when the ageing of the fleet opens the question its renewal, this might influence durably the dynamics of the fishery.

An assessment of the state of the fisheries of hake, red mullet and Norway lobster was carried out by using trawl survey data from the MEDITS research programme. The assessment was performed by means of the application of a composite model utilising the total mortality rate Z as a direct index of fishing effort. The studied area covered the whole western Italian coast (Ligurian and Tyrrhenian seas) and the eastern coasts of Corsica. The area was divided into twelve sub-areas, considered to be of similar ecological characteristics with similar initial productivity but considered to experience different rates of exploitation. Available information on fishing fleets and their geographic distribution was used in creating sub-areas. For each one of these sub-areas, the total mortality rates and a mean catch per unit of effort were estimated. The estimation of Z was performed by analysing the size structure of the cumulated catch in each sub-area and for each year. Catch rates were estimated as the mean catch per one hour of tow. The positioning of the current values of Z for the different sub-areas relative to the Z at maximum biological production suggests that, in most of the sub-areas, hake is in general fully exploited and red mullet overexploited. In the case of Norway lobster, it was not possible to obtain a statistically acceptable result probably due to a lack of contrasting enough levels of fishing pressure among sub-areas. The results obtained for hake and red mullet are in good agreement with the available information on the consistency of the fleets operating in the different sub-areas.

This paper presents a multispecific approach in order to assess the main demersal resources exploited off Senegal (West-Africa). In absence of reliable data on the actual fishing effort, two series of theoretical fishing effort are estimated, using available species abundance indices from 1971 to 1991. These two series correspond to different hypotheses concerning the trends of fleets' fishing power: an optimistic one and a pessimistic one. For each species or taxa, a surplus production model is calculated with landings statistics and effort. The combining of monospecific models provides a multispecific diagnosis. The analysis is completed by the calculation of diversity indices of catches at the equilibrium level, expressed as a function of fishing effort. While considering the uncertainty around this first assessment, we show that Senegalese groundfish resource is globally full or over-exploited, according to the considered hypothesis. Under the pessimistic hypothesis, 9 among the 11 taxa of Pisces were clcarly over-exploited, with fishing effort some-times as much as twice or three times the effort of maximisation (fMSY). The situation is very critical for Arius sp., Epinephelus aeneus, Pagellus bellottii and Pomadasys sp. Using the multispecific approach, pessimistic diagnosis indicates a fishing effort nearly twice fMSY, with a Maximum Sustainable Yield at about 53 000 t for the 11 taxa together. Conversely, in 1991, octopus and cuttlefish appeared under-exploited. The diversity analysis shows that an increase in fishing effort would lead to a decrease in catch diversity. This result is interpreted as a sign of fragility in the exploited ecosystem.

With slow growth rates, late maturity and a high maximum age of 100 years or more, orange roughy can be classified as a vulnerable deepwater fish species that can only sustain low rates of exploitation. Historical patterns of exploitation associated with this species suggest that it is currently not possible to manage its fisheries in the Northeast Atlantic sustainably, and the total allowable catch for orange roughy has been gradually reduced to zero for European fisheries since 2010. Orange roughy to the west of Ireland and Britain occurs on distinct bathymetric features (seamounts, hills and canyons) as well as on flat ground along the continental slope. Productivity-susceptibility analysis (PSA) was performed to evaluate the biological vulnerability of orange roughy in relation to other deepwater species and the risk that recent and current fisheries pose to its populations in the study area. Time-dependant PSA, based on the spatial overlap between orange roughy distribution and recent and current deepwater fisheries demonstrated a strong reduction in risk over time when fisheries stopped directed targeting practices and continued with mixed deepwater trawl fisheries. Some spatial overlap between the species and current fisheries remains, and while the method can show relative risk reduction, it cannot provide information on whether the risk is low enough to allow the recovery of depleted populations.

Common carp larvae were fed artificial diets over 28 days at about 24 °C. Diets were based on yeast and either beef liver or casein. Survival rates of larvae were 76-92% with liver diets and 87-96% with casein diets. Larval growth was superior with liver diets (mean final weights 720-880 mg) than with casein diets (130-340 mg). Within-tank coefficient of variation of body weight increased with mean weight according to a generalized S-shaped curve. The skewness coefficient tended to increase with the mean weight, with higher values in the casein-fed group than in the liver-fed group. It is concluded that liver is not strictly indispensable for carp larvae diets and may be replaced by less complex components.

A total of 324 specimens of the ommastrephid squid Todaropsis eblanae, collected from bottom trawl surveys in the North Sea was examined. Information on seasonal length frequency distributions and relationships of beak size to mantle length and wet body mass from the northernmost distribution of the species is supplied. The overall male: female ratio was 1: 0.78. Maturing males and females were found in winter and summer, while fully mature animals were observed only in summer. Sexual maturity in females occurred in bigger sizes than in males. Specimens were caught in water depths between 56 and 170 m throughout the whole investigated area except from the German Bight. This paper presents the first biological data on T. eblanae in the North Sea derived from scientific surveys.

The present work examines the usefulness of the combination of multivariate analyses and further one-way analysis of variance in the search for links between causes and effects in heterologous stimulation of spawning in fish. Stimulations with both 20 and 50 μg.kg–1 doses of [D Trp6] luteinizing hormone-releasing hormone analogue (LH-RHa) were effective in inducing and synchronizing spawning of red drum, Sciaenops ocellatus. Oocyte development monitoring using ovarian biopsy allowed treatment injections at different stages of maturation. The influence at stimulation time of female oocyte development state upon further development was shown. An interesting potential of second stimulation, leading to high quality spawns, was established and factors of success were identified. The best conditions for stimulation success were simultaneously late stage of oocyte development characterized by the beginning of oil droplet coalescence, high ovarian homogeneity quoted by the proportion of most developed oocytes in the biopsy sample, and low dose of hormone (20 μg.kg–1) for both first and second stimulations.

The process of sperm penetration into the egg of the European catfish Silurus glanis L. was investigated by scanning and transmission electron microscopy. Unfertilized ovum membrane under the internal micropylar aperture shows a critical depression with undulation and short microvilli corresponding to a specialized sperm entry site structure. Twenty seconds after insemination, the fertilizing spermatozoon fused with the egg at this specialized structure, without formation of an earlier fertilization cone, which had been confirmed in eggs of other fish. A cytoplasmic eminence developed however, immediately under the fused sperm head and then disappeared with time after fertilization to form a circular area around the fused sperm head, which in turn became embedded in the circular area with shortening of the flagellum. The micropyle in the catfish egg consisted of a micropylar vestibule and a canal, the internal micropylar canal being wide enough to permit the penetration of only one spermatozoon.

On the basis of hydrological and biological data collected between 1983 and 1987 along the Frenchcoast, and especially in the southern approaches to Brittany. it has been possible to compare differentparameters in an attempt to explain the seasonal variations of a toxic dinoflagellate: Dinophysis sp.speveral species were identified and their seasonal distribution patterns are described. The origin of the blooms, from either coastal endemic or offshore populations, is considered

Several pelagic fish species are known to associate with floating objects. However, quantitative information on the main factors that drive this associative behaviour is still lacking. Small pelagic fish offer a particularly interesting case study for this phenomenon, since the small spatial scales involved in their association with floating objects allow experimental data to be collected at a fine scale. Here, we monitored twelve acoustically-tagged bigeye scads, Selar crumenophthalmus (Carangidae), (mean fork length 16.4 cm, SD 2.1 cm) around a floating object moored in shallow water (15 m depth) playing the role of a coastal fish aggregating device (FAD). To quantify the role played by variations in current and daylight, we calculated the speed distribution, pair correlation function and group polarization for the tagged fish hourly, from midday to dusk (13:00–18:00), for varying current strengths and daylight conditions. We found that the current induced a shift in the position of the aggregation upstream of the FAD, at distances that increased with the current strength. We found evidence of an expansion and a higher coordination in the aggregation at dusk, with increasing speed, distance among conspecifics and alignment. We discuss possible scenarios in which group polarization increases at dusk and suggest complementary measurements for future experiments that could confirm our findings.

Fisheries libraries in R (FLR) is an open-source software framework based in the R statistical software environment, with the main purpose of allowing for the efficient simulation and evaluation of fisheries management strategies. This paper details a generic (non-spatial) biological operating model used to simulate populations and their reaction to fishing, and an observation error model and methods for simulating structured sampling/observation error and bias in key fisheries assessment indices. It also contains the details of how the candidate harvest control rules, based on survey-derived information, can be characterised and implemented, and how the processes of management strategy evaluation and stock assessment can be included in the simulations.

The reproductive characteristics of Oreochromis niloticus, a multiple spawner, have been compared between populations submitted experimentally to three types of spatial structure. Fish from a same original stock were divided and reared for 2 months in: 1) concrete tanks with a bare bottom, 2) concrete tanks with a sandy bottom, or 3) concrete tanks equipped with an artificial reef. The females were then killed and their gonads examined for sexual stage and fecundity determination. Fecundity was inversely correlated to the spatial complexity of the environment whereas oocyte size tented to increase together with spatial complexity. Females placed in tanks with artificial reefs presented a lower fecundity and reproductive investment and bigger oocytes than those maintained in the bare bottom tanks. Fish reared in tanks with a sandy bottom had intermediate reproductive traits. The response of females to changes in the spatial structure of their environment was observed after only one or two reproductive cycles, providing the first experimental evidence of such rapid phenotypic adaptation to environmental complexity. The results also indicate that the perception of living space, arising from the availability of refuges and spawning sites, is more likely to influence the reproduction of tilapias than substrate quality.

Dramatic declines in American eel (Anguilla rostrata) recruitment haveresulted in strong conservation measures being implemented. Recovery actions in Ontariohave included stocking of glass eels. Given the financial costs and imperative toundertake effective recovery actions, post-stocking monitoring is essential. In thisstudy, point- and transect electrofishing sampling were compared in terms of eeldetection, catch rates, size-selectivity, and power to detect changes in abundance.Transect sampling was more likely to detect eels and captured over twice the number ofeels than point-sampling. Differences in catch rates and statistical power were dependenton the catch-per-unit-effort measure (i.e. sampling unit vs. time). Results support atransect-based sampling program for stocked eels in Lake Ontario tributaries.

Moored FADs (MFADs) have been a key area for development in Guadeloupe (Lesser Antilles) since the late 1980’s. The main objectives underpinning the development of MFADs were to (i) reduce fishing pressure on coastal fishing resources; (ii) boost fishermen’s incomes; and (iii) increase local consumption of locally generated fishery products as a proportion of overall consumption. This paper gives an overview of the current structure of Guadeloupe’s fishing fleet and fisheries, with a specific focus on MFAD fleets in a relatively unstructured environment with regard to regulation, and so how these fleets operate in a context of unrestricted development of private MFADs. In addressing the following key issues, this paper aims to: assess the economic performance of fleets operating on MFADs, understand why the MFAD fishing activity has not developed more than it has, and suggest how better MFAD management could improve the situation. Socio-economic information on a trip and fleet level basis were collected and stored on a fisheries information system to analyse the relative attractiveness of MFAD fishing and assess the overall economic performance of MFAD fleets as compared to other non-MFAD fleets. Non-monetary variables were also tested to explain the degree of dependence on MFADs. In 2008, economic returns from FADs were relatively low, both in terms of wages for the crews and in terms of profit for vessel owners. Earnings were higher than coastal fishing activities, but seem to have been very sensitive to the indicators used in our analysis. MFADs are expected to become much more attractive as a result of MFAD regulation, especially through the establishment of collective MFADs.

Plasma and pituitary gonadotropin (GtH) levels, and the gonadotropin releasing hormone (GnRH) in differents areas of the brain, were measured using radioimmunoassays during the prespawning and the spawning period in a wild population of roach (Rutilus rutilus). GtH pituitary levels did not vary. On the contrary GtH plasma levels showed variations during the prespawning period and were minimum on the day of arriva1 on the spawning areas, Do. During spawning they increased in ovulated females but also in unovulated animals and returned to low values, 1 month after. During this period GnRH varied inversely in all brain structures and was always negatively correlated with the blood plasma GtH levels. This suggests that all the brain GnRH would be involved in the control of the GtH secretion during spawning. This was not the case during the prespawning period, during which only hypothalamic and pituitary GnRH levels were correlated with GtH. There were also marked variations in the telencephalic GnRH extra hypothalamic GnRH. It is hypothetized that it could be a link between environmental factors and the hypothalamo-pituitary cornplex.

The pattern of ammonia excretion was examined in the Siberian sturgeon, Acipenser baeri, during starvation. For different weight groups (60 g to 2 kg), this excretion decreased rapidly to reach a constant level of 32 mg NH4-N.kg-1.day-1 after 8 days of fast. This minimum is an estimation of the Endogenous Nitrogen Excretion (ENE). No diurnal pattern was observed in the ammonia excretion or oxygen consumption (28.6 ± 3.2 mg O2.kg-1.h-1, mean ± sd) of fasted fish. These data appear to indicate that the basal metabolism is very low in the Siberian sturgeon and that the nycthemeral cycle is only the result of exogenous nutrition.

The results of preliminary experiments in the development of a hatchery brood stock of whitefish of Lake Geneva, Coregonus shinzi palea Cuv. and Val. (lavaretus), are described. Factors likely to influence the date of spawning and the quality of eggs were studied by reference to the performance of wild spawners from the Lake Geneva. Fish were reared in tanks and the ovulation of females occurred spontaneously at the same spawning time as in wild spawners from the lake. Reared females have produced 30 000 eggs/kg against 45 000 in wild fish. The survival rate of a domestic egg was about 10% less than that of wild females. Since the overripening of the ova was rapid it was necessary to check the ripe females twice a week. The exposure of fish to long days in autumn delayed spawning by two months and permitted the synchronization of hatching under optimal conditions of growth. The ovulations were spread over a period of 3 months when the fish were subjected to long days until spawning. In contrast, termination of the long day regime in December induced a synchronization of the ovulations over just one month.