The sea cucumber stocks off the east and northwest coasts of Sri Lanka were estimated bysurveying 1307 km2 and 1779 km2 by an underwater visual census (UVC)in June and October 2008 respectively. The presence of twenty-five sea cucumber speciesbelonging to seven genera; Actinopyga, Bohadschia, Holothuria, Pearsonothuria,Stichopus, Thelenota and Acaudina was identified in fivehundred sampling sites randomly selected in each area. The overall average density (± SD) of sea cucumbers was higher in the northwest (350 ± 648 ind ha-1) than inthe east (90 ± 130 ind ha-1) and low-value species were predominant in bothsurvey areas (79 ± 125 ind ha-1 in the east, 244 ± 488 in the northwest) whencompared with medium (10 ± 34 ind ha-1, 105 ± 175 ind ha-1,respectively) and high-value category (<2 ind ha-1).The estimated total biomass in the northwest (13 024 t) was roughly four times greaterthan the east (3027 t). Holothuria edulis was the most abundant speciesin numbers while Holothuria atra had the highest stock biomass in bothareas. Sea cucumber densities were significantly different among the habitat(p < 0.001) and depth categories. The highestdensity was reported in rocky habitat associated with seagrass and / or macroalgae. Thedensity of low-value species was significantly high in 1–10 m depth category(p < 0.001) in the northwest while othercommercial groups were dominant in 20–30 m depth range in both areas. Temporal banning ofthe fishery for high and medium-value species would be a better management option to avoidfurther stock depletion.

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.

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.

The phospholipid composition and fatty acid characteristics of diacyl and plasmalogen forms ofphosphatidylcholine and phosphatidylethanolamine of sperm of five marine and five freshwater speciesof fish have been determined. There was considerable variation in composition within each group offish, which obscured any differences which are related to the osmotic environment. Since such factors as temperature, nutrition, etc. probably greatly influence the lipid composition, we failed to determine a relationship between osmolality and phospholipid composition. We have also found certain phospho-lipid peculiarities, characteristic of sperm of various species of fish.Nevertheless, as we have found previously, the molar ratio of cholesterol to phospholipids in fishsperm is determined by the salinity of the habitat.

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.

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.

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.

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.

Catchability is crucial for the economic performance of fisheries and their management. However, in many bio-economic simulation models it is assumed to be either constant or it is largely ignored, despite the fact that it is known to vary due to technical, environmental and behavioral factors. Such variation can cause the relationship between effort and fishing mortality to be nonlinear. This paper provides evidence for the possibility of nonlinear optimizing behavior from the Dutch beam trawl fishery, provides a methodology for estimating the curvature of the resulting relation, and a simple way of implementing these processes within a bio-economic model. Moreover, it shows the influence of a nonlinear relationship between effort and fishing mortality in a model of effort management (EU long-term flatfish management plan).

In order to address critical gaps arising from limited available data on historic shark catches in the Atlantic Ocean, a method was developed to estimate shark removals using shark fin trade data. A characterization of the global fin trade as of 2000, including number and biomass by shark species, was used as the basis of the methodology. A first step involved scaling Hong Kong trade-derived estimates for 2000 to annual global values for 1980-2006 based on the observed quantity of imports to Hong Kong and an approximation of Hong Kong's share of the global trade in each year. The resulting global fin trade figures for each year were then scaled to Atlantic-specific values using three different factors: (1) area of the Atlantic range relative to the global range of pelagic sharks; (2) Atlantic catches of tunas and billfishes relative to global catches of tunas and billfishes; and (3) Atlantic longline effort relative to global longline effort. The strengths and weaknesses of each scaling factor and the assumptions inherent in the methodology are discussed. These estimates are not intended to replace reliable fisheries dependent catch data compiled by ICCAT from submissions of members and cooperators, but can serve as one of a variety of useful cross-validation tools when historic catch data are missing or uncertain.

In aquaculture, a diet both nutritionally sound and organoleptically pleasing is essential to guarantee satisfactory intake. This has not been fully achieved with soleids (Solea solea and Solea senegalensis) because of their special palatability requirements, which are difficult to satisfy with conventional diets. Nevertheless, soleids have long been considered interesting species for aquaculture. To improve the palatability of diets for this family, various substances have been tried. Betaine has been the most effective substance by far, for all the species studied and especially for sole, reporting good results but at too high a cost. In other areas of animal production, the problems of palatability are solved with commercial flavours, which offer scope for specialisation to satisfy the most demanding organoleptic requirements. The aim of the present work is to evaluate the use of a bivalve commercial flavour as an alternative to betaine in sole diets. An ethological methodology, adapted to the feeding behaviour of sole, is developed to qualify and quantify behavioural changes when faced with experimental diets containing either this commercial flavour or betaine. Results show that the commercial flavour externally applied to feed particles performs efficiently as an attractant and as an arrestant, being able to attract the animal to the food source from some distance, provoke the ceasing of locomotion close to the food particle and promote initiation of feeding. In this step of the feeding sequence, it may be considered a viable alternative to betaine from the organoleptic point of view and economic cost. When the commercial flavour is applied internally to the feed, its performance as a stimulant, to encourage the continuation of feeding, is not distinguishable from betaine. Other factors such as time of feeding and size of fish, also assessed in the experiment, boldly influenced the level of acceptation of diets, even more than the composition of the diet itself. The distribution of feed at a time out of the endogenous rhythm of the species provoked a lower feed acceptation. Slight differences in the size of fish also affected the degree of acceptation, this being lower in the smaller fish.

L'étude de la croissance linéaire, rapportée au modèle particulier de von Bertalanffy, de l'espèce Epinephelus guaza échantillonnée dans le canal sicilo-tunisien donne : L∞ = 114,49 cm ; K = 0,0928 ; t0 = -0,7508 an, et la relation entre la taille et le poids : Log Wi = 3,073 Log Li - 4,377. Le taux de croissance présente un infléchissement significatif à l'âge de 5 ans qui traduit une réorientation de l'allocation énergétique du métabolisme vers une activité gonadique ovogénétique (maturité sexuelle). Ce poisson hermaphrodite protérogyne manifeste ensuite, à l'échelle de la population, une inversion sexuelle qui se produit entre 9 et 16 ans avec un maximum d'intensité à 12 ans. A partir de cette période d'inversion, la dispersion des tailles corporelles à l'intérieur de chaque classe d'âge s'amplifieau point qu'il devient probablement illusoire d'utiliser les paramètres de croissance comme critères d'identification des unités de population. Des critères issus de l'étude du développement sexuel et replacés dans des analyses démographiques qualitatives et quantitatives menées conjointement pourraient se révéler plus performants.

This work focuses on investigating the potential of calcein and manganese as growthmarkers of the common cockle (Cerastoderma edule) in the bay of Somme(France). Recapture of shells, previously marked using a chemical marking and then bred innatural conditions, was performed in order to determine the shell growth patterns. Calceinmarking has shown a fluorescent increment in shells after only 30 min immersion time at150 mg L-1, but also for shells immersed 3 h at 50 mg L-1. Likewise,manganese shell marking was revealed under cathodoluminescence for shells immersed 1 h at120 mg L-1 as well as for shells which spent 4 h at 90 mg L-1. Anumerical analysis performed on each marked cockles has revealed 23 micro-incrementsbetween the mark and the ventral edge of the valves, corresponding to the 23 tides thatoccurred during the 12 days at liberty post marking. The periodicity of incrementformation is thus validated for a tidal frequency. The growth rates of C.edule, ranged from 11.67 to 19.94 μm d-1, decreasedsignificantly with increasing shell length. This preliminary study gives a clue to theunderstanding of cockle growth and could be used in shellfish production for cockle agemonitoring, but also for chemical analysis to learn more about biomineralization processof this species.

Water Framework Directive requires reliable and effective monitoring tools, and hydroacoustics has a potential to be one of them. The effect of pulse duration on in situ acoustical estimates of fish density and their size distribution was investigated. Measurements were performed in the oligo-mesotrophic Lake Hancza (Poland) using a SIMRAD EK60 split-beam echo-sounder at 70 kHz frequency. During the survey, two similar transducers pinged alternatively through the multiplexer using 4 different pulse lengths, from short to long ones. The results show that the volume backscattering coefficient (Sv) values, equivalent of the fish biomass, were not influenced by the pulse length. However, the number of the detected fish, the mean target strength (TS), and consequently the fish density, differed significantly for the long pulse duration data. This was especially noticeable in the layer above the thermocline with dense fish populations. In this upper layer, for the long pulse the Sawada index frequently exceeded value of 0.1 leading to overestimation of the mean TS and underestimation of the fish density.

Taking into account that the relationship between metabolic substrate and the characteristics of the diet is essential for understanding the mechanisms associated with the use of the components of a certain food substance, the aim of this study was to examine the metabolic substrate used by Penaeus setiferus, P. schmitti, P. duorurum and P. notialis postlarvae PL 35–40 (35–40 days after metamorphosis) fed purified diets with different levels of proteins (40, 50, 60 and 65%). Oxygen consumption and ammonia excretion were measured in animals in intermoult which had been acclimatized to each diet over a minimum of 5 days. Measurements were taken on fasted (24 h) and fed animals. Oxygen consumption of fasting animals increased with a rise in the proteins of the diet in the four species. In the fed animals, this tendency was observed in P. setiferus and P. notialis, while in P. schmitti and P. duorarum oxygen consumption was a weak relationship, decreasing or increasing with a diet with 50% protein. Both in fasting and feeding animals, the ammonia excretion increased with the increase in proteins in the diet. The O : N atomic ratios of the four species decreased (between 30 and 3), according to increase in dietetic protein : energy ratio, (10.4 to 17.0 mg protein/kcal). The highest value of O : N ratio was observed in P. setiferus (40% of protein requirement, O : N = 24 to 34) and lowest in P. schmitti (60% of proteinrequirement, O : N = 4 to 11), with intermediate values in P. duorarum and P. notialis (50% protein requirement, O : N = 8 to 14 and 13 to 19, respectively). These results support previous research that showed that the omnivorous-herbivorous species, like P. setiferus, use protein-lipids normally as energy source in contrast to omnivorous-carnivorous species such as P. duorarum which use protein preferentially as a source of energy.

Tilapia species are generally characterized by a large tolerance to salinity; however, such capacity to adapt to brackish or seawater may be modulated by environmental factors. The major osmoregulatory mechanisms involved in salinity adaptation are presented. Most of the available data concern the role of gills in salt or water exchange. The importance of different factors (environmental or endogenous) in such adaptation is also discussed. The second part presents a survey of the endocrine control of osmoregulation in tilapia. Both fast-acting (e. g. glucagon, urotensins, catecholamines) and long-acting (e.g. prolactin, cortisol) hormones have been studied. In conclusion, several areas of osmoregulatory physiology potentially interesting for aquaculture are discussed.

The early debate concerning the existence of several self-sustaining populations within the distributional limits of marine species centered on Atlantic herring in the northeastern Atlantic. Fr. Heincke convincingly resolved the controversy by extensive sampling of herring and sprat for the analysis of a large number of meristic and morphometric characters, and the development of new statistical methodology (including rudimentary multivariate statistics). He initially analysed the morphological variability at different parts of the life cycle of spring – and autumn – spawning herring aggregations off Kiel. This detailed study was accompanied by somewhat less-detailed sampling of herring and sprat from other locations in the Baltic Sea, North Sea, and Norwegian coastal waters. Heincke argued that a fundamental shift in both the species concept and the mechanism of speciation was required to account for the emerging empirical observations on marine fish. His observations and conclusions on the nature of geographic variability of fish species, even though revolutionary, were accepted rapidly. The influence of his studies on fisheries research, systematics, and evolutionary biology are evaluated. In addition, the contributions of J. Schmidt and J. Hjort to population thinking are briefly addressed. It is concluded that the studies by Heincke on herring populations, as well as having a major impact on subsequent developments in fisheries biology and management (in essence the definition of management units based on geographic populations or population complexes), also had an important impact on the biometricians (Weldon, Pearson) and the development of the evolutionary synthesis in the 1920s and 1930s (through Chetverikov, Dobzhansky, and Goldschmidt). Observations on geographic patterns in populations from terrestrial systems could be generalized to the oceans on the basis of Heincke's quantitative studies on herring and sprat (and the follow-up work on other fish species).

These early investigations on the very existence of marine populations by Heincke, Hjort and Schmidt are still pertinent to recruitment research and the studies underlying the definition of management units. An historical perspective may contribute to the resolution of present topical issues involving the regulation of populations.

The paper summarizes aspects of nutrition and growth in Clarias species. Of the many Clarias species cultured, Clarias gariepinus has been subject to particularly intensive research; the species has been widely introduced for aquaculture outside its natural range. Clarias are omnivorous fish. Their dietary protein requirements are about 40%, their energy requirements range between 13 and 17 kJ.g−1. Controversy exists on their ability to utilize carbohydrates, despite the fact that their natural feed may contain high levels of carbohydrates. Comparison of growth performances as recorded in literature indicate that C. gariepinus seems to perform better in terms of growth rates and feed conversion than other species (C. isheriensis, C. batrachus, C. fuscus). Monosex culture (in C. gariepinus) or triploidy (in C. gariepinus and C. batrachus) do not seem to hold much future for improving growth and feed utilization, in contrast to hybridization. Selection for improved growth could have drawbacks, such as an increased level of agression. To achieve improved growth, selection for lower maintenance requirements or better glucose metabolization seems preferable over selection for high feed utilization efficiencies.

The reproductive dynamics of swordfish (Xiphias gladius) was investigated from catches of the Reunion Island-based longline swordfish fishery between 19–25 °S and 48–54 °E. Thus, 1727 swordfish (size range 75–289 cm, lower jaw-to-fork length, LJFL) were sampled on board commercial fishing vessels during the period of May 1998 to January 2001. Reproductive activity was assessed using macroscopic gonad characteristics, trends of gonadal indexes for both sexes, oocyte size-frequency distributions and microscopic investigation of oocyte development stages. Size at first maturity (L50) for female and male swordfish was estimated in Indian Ocean for the first time. L50 was estimated at 170 cm and 120 cm (LJFL) for females and males, respectively. Spawning occurred from October to April in the vicinity of Reunion Island where sex ratio of caught populations fluctuated seasonally. The seasonal changes in sex ratio and the incidence of larger individuals at the beginning of the spawning season provide some preliminary indications of synchronized movements of swordfish between spawning grounds and neighboring regions. Our results add significantly to knowledge about the reproductive biology of swordfish in the southwestern Indian Ocean. An overview of the available information on reproductive biology and dynamics of swordfish in Indian Ocean and eastern Pacific indicated that spawning activity is localized in discrete areas, and showed that there is incomplete information on spawning grounds in this extended area.

To better understand the effects of perturbations (e.g. global change) or habitat restorations on fish population dynamics, it is crucial to improve the knowledge about strategies of habitat use (especially in terms of velocity use) by fish. Many recent studies accurately describe kinematics or energetic budgets of swimming activities, which are often species-specific and hardly transferable to other species. The main goal of the present study was to revive more general ecomorphological relationships between body shape and strategies of velocity use by highlighting a functional aspect of fish morphology: the hydrodynamic potential. For this purpose, potential relationships between minimum drag coefficients (Cdmin, constant at high Reynolds numbers), velocity use, fish morphology and drag in given flow conditions were investigated. To assess these relationships, dead drag values (i.e. drag values measured on dead, straight individuals) of 27 riverine species (108 individuals in total) common in France were experimentally measured under various flow conditions. These values served to estimate the Cdmin of fish. For pelagic species, Cdmin values were related to both preferred and near-maximum flow velocity used by the fish in nature. Explaining 61% of its variability, Cdmin was described using six morphological variables, which demonstrates the functional link between fish morphology and velocity use. For all studied species, a model explained 94% of drag variability using the Reynolds number of fish and three morphological variables. The link between morphology and drag force at given velocity conditions provides simple elements for modelling fish energetics in the context of physical habitat use. Moreover, the relationships between fish velocity use and their Cdmin open many applied perspectives, such as assessing the species abilities to withstand discharge modulations.