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.

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 functioning of estuaries relies on a natural dynamism imposed on these systems by riverine and marine influences. The increasing abstraction of fresh water from both large and small river catchments in southern Africa has had the effect of forcing some estuaries into artificial cycles, i.e. natural successions now have human imposed trajectories that are changing estuarine variability and forcing some systems into extreme states. The ichthyofauna has responded to these changes in a variety of ways. Where river flow has declined considerably, or ceased altogether for extended periods, fish recruitment has shown a considerable decrease. This can be related to the collapse in planktonic productivity which negatively affects zooplanktivorous fishes, as well as decreased amounts of olfactory cues entering the sea for the attraction of larval and juvenile marine fishes into these estuaries. Hypersaline conditions can result in both a reduced species diversity and abundance. However, where estuaries lose their normal estuarine salinity gradient and become “arms” of the sea, there is often an increase in fish species diversity due to stenohaline marine taxa entering the estuary. Unfortunately the gain in small numbers of marine stragglers is insufficient to compensate for the decline in estuarine dependent fishes that usually dominate these systems. Conversely, major river flooding often causes temporary decreases in both species diversity and abundance due to a rapid decline in salinity, increased suspended sediments, reduced dissolved oxygen levels, and a collapse in the availability of pelagic and benthic food resources. However, the “resetting” of estuaries by episodic events is part of the essential cycle that maintains and enhances estuarine productivity and habitat diversity. Recovery by estuary associated fishes from such events is usually rapid and linked to a variety of factors, especially estuary morphometry which has a direct influence on the flushing or retention of estuarine biota. Freshwater flows interact directly and indirectly with the fishes that inhabit estuaries, e.g. river floods directly influence estuarine morphometry, water temperature, salinity, pH, turbidity, nutrient status, organic inputs, dissolved oxygen concentrations and olfactory cues; and indirectly affect mouth status, tidal prism, habitat diversity, primary and secondary productivity, fish recruitment, food availability and competition. Depletion or removal of components of river flow to an estuary have major short and long-term negative impacts on the ichthyofauna, some of which can be ameliorated by the provision of an environmental freshwater allocation that is appropriate to that particular system.

The level of genetic differentiation between anadromous and non-andromous trout (Salmo trutta L.) coexisting in a Norman river (Oir river) was examined at 15 microsatellites markers. Despite a large amount of variation, no genetic differentiation was found between forms. Four domesticated stocks were also genotyped with the same loci. Highly significant differences were found with natural samples allowing to exclude a recent stocking effect on the Oir population. We conclude that the resident and anadromous trout form a single naturally reproducing unit in this river system. However, this conclusion could reflect particular ecological or demographic conditions in the Oir basin and needs to be validated in other hydrographical and ecological contexts.

Determining the timing or frequency of movement of fish and the relative importance of different habitats is difficult. Advances in otolith chemical techniques and interpretations (including elemental ratios and stable isotopes) suggest that this is a powerful method for determining movement of fish. To date, the majority of applications have involved marine fish, however, otolith chemistry has the potential to determine movements of diadromous and freshwater fish; I therefore review freshwater applications of otolith chemistry in this paper. Despite some limitations regarding strontium:calcium (Sr:Ca) ratios (e.g. Sr concentration of the water is not always measured, Sr:Ca ratios in freshwater can exceed marine waters, and mixed results for the relationship between otolith Sr and salinity), they have been widely used for a variety of applications involving diadromous species and more recently freshwater fish. In addition, barium:calcium (Ba:Ca) ratios have recently been used to determine movements of diadromous and estuarine species, as ambient ratios are possibly linked to environmental flows. Several studies have also investigated the use of multielemental otolith composition to discriminate between groups of fish collected from different lake or river systems, but a wider range of applications are possible. Several applications of Sr isotopes have also been investigated, most of which is focused on salmonids (e.g. distinguishing fish from different river systems, determining movement history of individual fish). Relatively few studies have investigated the use of other isotopes (e.g. oxygen, sulphur) for determining movements. Otolith elemental ratios and stable isotopes have great potential to determine movements of freshwater species, with possible applications likely to increase as analytical technology improves.

Une analyse phylogéographique de quinze échantillons de Dicentrarchus labrax dont cinq sont originaires de Méditerranée occidentale, sept de Méditerranée orientale et trois échantillons d'élevage en provenance de trois piscicultures françaises a été effectuée à partir du polymorphisme de six locus microsatellites. Parmi les échantillons orientaux, trois ne se regroupent pas en fonction de leur origine géographique, mais plutôt avec le groupe occidental. Ces échantillons présentent également une diversité allélique légèrement réduite, indiquant qu'ils proviennent d'un nombre limité de géniteurs d'origine occidentale. Parmi les stocks d'élevage, un seul montre une réduction significative de la variabilité génétique, ce qui indique que ces cheptels sont ouverts et font largement appel à des géniteurs sauvages. L'utilisation d'alevins d'origine occidentale pour ensemencer les premières fermes d'élevage du bassin oriental remonte au plus tard au début des années 80. Ceci soulève la question des mécanismes biologiques expliquant le maintien de poissons d'origine occidentale dans un contexte oriental pendant au moins deux ou trois générations.

Age and size-at-maturity of Loligo vulgaris from Portuguese waters were evaluated in order to explain its complex population structure, which is strongly influenced by continuous spawning. Age was obtained by increment counting in statoliths. Maturity ogives by age group indicated that males mature one month earlier (at 277 days) than females (at 298 days). Females mature at a ML50% of 17.6 cm, while males mature at smaller sizes. The later, however, showed a high degree of complexity in the size at maturity with evidence of two size at maturity groups. In both sexes, maturity was ultimately found to be primarily dependent on size rather than age. The effect of hatching season on age-at-maturity, size-at-maturity and reproductive investment was analysed by comparing two groups of squid hatched under distinct environmental conditions, namely the temperature during the first 3 months of life, the cold cohort (CC), hatching between December and March and the warm cohort (WC), hatching between May and September. Significant differences were found between cohorts on age-at-maturity, size-at-maturity and reproductive investment, giving indication of the environmental influences on sexual maturity. CC squid mature ca. 2 months later in life than WC squid and at a significantly larger size. The reproductive investment as measured by GSI was higher in the WC squid. Much of the variability in age and size-at-maturity of females in the population was due to differences between cohorts but this was not the case for males.

To evaluate the population structure of Ucides cordatus in the Caeté estuary, crabs were sampled bimonthly over 13 months in three Rhizophora mangle forest stands that differed in their accessibility and fishing history. Additionally, sex- and size composition of the commercial catch and catch per unit of effort (CPUE – the number of crabs captured per fisherman per day) were monitored between 1997 and 2003. Average and maximum crab sizes (carapace width, CW) from all three sampling sites combined were 6.1 cm and 8.8 cm in males, respectively, and 5.5 and 7.3 cm in females. Crabs were largest at the site that had been reportedly less exploited in the past. The overall sex ratio was skewed towards males (53−62%). Egg carrying females were only encountered during the rainy season. Mean crab abundance and biomass was 1.7 specimens m−2 and 142 g m−2 fresh mass. Only large males were commercially harvested (98% ≥ 6.5 cm CW). Their biomass was 53 g m−2 and the Caeté estuary yields an annual production of 1200 t of these large specimens. This is approximately the quantity that is currently being harvested. CPUE was similar in 1997 and 1998, then decreased by 15% until 2000 and stabilized for the rest of the study period. Mean capture size (cm CW) ranged between 7.2 ± 0.5 and 7.5 ± 0.2 and was above the size of 50% (and even 100%) male maturity and the legal minimum capture size. There is no evidence that the Caeté crab population is overfished, despite over 30 years of de facto open access exploitation. Apparently, the selectivity of fishermen and consumers for large male crabs as well as the local artisanal capture techniques are key factors in preventing an overfishing of the Caeté crab population until today. Our results suggest that the economic and social sustainability of this fishery will be affected well before the biological one, which should be considered in the recently proposed coastal co-management plan for the region.

To understand the mechanisms that influence recruitment of the commercially important chokka squid Loligo vulgaris reynaudii, knowledge of its early life history is required. This paper evaluates the influence of food supply on yolk utilization, metabolism and growth of paralarvae. Eggs collected on the spawning grounds were incubated and the paralarvae reared in the laboratory under “fed” and “starved” conditions for 22 d at 16 ± 1 °C. Some paralarvae lasted 42 d in the laboratory. Mantle length (ML), wet and dry weights (WW and DW) and yolk weight (YW) were measured daily from samples of ~30 (10−51) paralarvae from each group. Yolk weight was estimated using image analysis to determined yolk volume. Three methods (growth model, O2 consumption rates and yolk utilization rates) were used to estimate metabolic rates. Input parameters included daily mean wet weight of paralarvae and temperature. Mean ML, WW, DW and YW at hatching were found to be 2.3 mm, 1.86 mg, 0.45 mg and 0.21 mg, respectively. The experiment revealed that daily yolk utilization rates were 86 and 95% d−1 for fed and starved paralarvae respectively, and that the yolk reserve was almost exhausted 3−4 d after hatching. Starved paralarvae survived for 6 days (with 80% mortality), while fed paralarvae attained a growth rate of 7.8% body WW d−1 over the first 22 days after hatching. Results illustrate that temperatures on the chokka squid spawning grounds allow paralarvae to grow at the fastest rates possible without being subjected to a growth “slow down” caused by a high temperature dependent imbalance between sustaining high metabolic and commitment high feeding rates.

The nuclear DNA content in Dicentrarchus labrax, Sparus aurata, Liza ramada, and Anguilla anguilla, was measured by flow cytometric analysis. Male human leukocytes were used as internal reference cells. Nucleated fish erythrocytes were stained simultaneously to human leukocytes with a staining buffer containing propidium iodide (PI). Nuclear DNA contents of target species were estimated in relation to an assigned value of 7.0 pg DNA for male human leukocytes. The DNA content/nucleus (±CI) was 1.55 ± 0.02 pg for D. labrax, 1.90 ± 0.03 pg for S. aurata, 1.57 ± 0.02 pg for L. ramada, and 2.43 ± 0.04 pg for A. anguilla. Intraspecific DNA content variations ranged from 0-9% and averaged around 4% in all taxa. The results did not evidence significant differences in genome size between males and females in either D. labrax or L. ramada. / Anguilla anguilla

The main purpose of this study was to establish the pattern of variability of some hemato-immunological parameters in the mangrove oyster, Crassostrea rhizophorae, from 3 different environmental conditions in Santa Catarina Island: two natural habitats (mangrove and rocks of the coastal bay) and one oyster culture station. The water quality was adequate in all localities. The animals were collected seasonally over a period of one year (n = 30, per locality). The oyster hemolymph comprised two basic cell populations, hyaline (HH) and granular hemocytes (GH). Both cell populations contained carbohydrates and glycogen in their cytoplasm (periodic acid Schiff reaction, PAS staining) and the occurrence of lysosomes was suggested by the detection of acid phosphatase (Gomori's method). Both hemocyte populations were able of phagocytosis of zymosan particles in vitro and producing cytotoxic molecules, such as the superoxide anions (nitroblue-tetrazolium, NBT reduction). The oyster hemograms significantly differed in the different habitats and also among seasons. The total circulating hemocyte counts (THC) and the percentage of GH in the mangrove and rock oysters always differed from each other, but not from those of the cultured oysters. The highest THC and the lowest percentage of GH were always found in summer. The total plasma protein concentration (PC) exhibited a similar seasonal pattern in all oyster populations, with a marked decrease in spring. The PC of the cultured oysters was almost always significantly lower than that of the other oyster populations. The plasma agglutinating titer was higher in the cultured oysters regardless of season. The histological organization of the oyster digestive gland and gills was basically similar to that of other oyster species. Their structural aspect did not show any detectable alteration, corroborating that the oysters were in good health. The results of this study will serve as a basis for further analyses on the monitoring of C. rhizophorae health status and environmental quality in different aquatic habitats.

Marine fisheries and the ecosystems that sustain them are increasingly beset by environmental deterioration, and the problem is particularly acute in coastal zones where human populations are increasing. In the best of circumstances, fishery managers are faced with the multiple, often conflicting, demands of resource users, politicians, and scientists when considering strategies for resource management. A further challenge is that management decisions must be made against a backdrop of a deteriorating environment and the shifting status of coastal ecosystem integrity. Traditional tools for single-species management may be inadequate in these settings. Furthermore, the necessary empirical data to appropriately parameterize models with vital rates representative of an altered environment are often lacking. Thus, we need approaches that better approximate the complicated dynamics between environmental conditions, fishery impacts, and multi-species interactions. Spatially-explicit, individual-based simulation modeling potentially permits this kind of integration, but it has seen limited use in marine resource management, especially with respect to benthic resources. My colleagues and I have used this approach, combined with targeted experimental work, to explore the impacts of nursery habitat deterioration, coastal freshwater management, and fishery activities on Caribbean spiny lobster populations and sponge community structure in the Florida Keys, Florida (USA). Although not applicable for all resource management situations, our experiences provide an example of the potential use of spatially-explicit, individual-based modeling and targeted empirical science in predicting resource conditions in a dynamic environment.

This research investigates a status assessment approach for remnant lake salmonin populations, using the lake charr (Salvelinus namaycush Walbaum) of Crean Lake (105 km2) as an example. A mark-recapture program was implemented employing small-mesh gill nets to ensnare charr by the teeth at spawning. Prior to sampling, potential spawning sites were designated primary or secondary based on habitat. Most charr were caught on three primary reefs, with some spawners moving between reefs. The spawning period peaked at day 2, enhancing spawning synchrony, and lasted up to 10 days. Results produced very low sampling mortality (5.7%), consistent estimates of the number of spawning charr ( $\sim $ 60 y−1) and a very low (<2000) estimate of the total number of mature charr in Crean Lake. The approach offers an effective means of assessing remnant salmonins with minimal impact on their populations.

Five polymorphic microsatellite DNA loci were identified in Labeo dero (Hamilton Buchanan), through cross-species amplification. Thirty-one primers developed for three cyprinids were tested in the study. The genetic variation detected at each polymorphic microsatellite locus was analysed. Significant genotype heterogeneity indicated that the samples are not drawn from same genepool. The identified microsatellite loci exhibited promise for use in fine scale population structure analysis of L. dero.

In order to understand the morphological differences between four populations of genus Coilia (Teleostei: Clupeiforms) and identify them conveniently, truss network data were used to conduct multivariate analysis. Nineteen morphometric measurements were made for each individual. Burnaby's multivariate method was used to obtain size-adjusted shape data. The cluster analysis and discriminant analysis were used to discriminate among populations. The results indicated that 1) the four populations were clustered into three distinct groups; the first group included Changjiang C. mystus and Taihu C. ectenes, the second one included Zhujiang C. mystus, the last one included Changjiang C. ectenes, and 2) discriminant analysis with selected 4 morphological parameters showed that the identification accuracy was between 88% and 100%, and global identification accuracy was 95%. Our result showed that populations of different Coilia species living in geographic proximity to one another are more similar than conspecifics living farther apart. Separation and adaption are important to morphological difference. The taxonomy of genus Coilia should be reconsidered. This study also showed that the method to obtain size-adjusted data is important to acquire right conclusion.

Domoic acid (DA), the toxin responsible for the illness known as amnesic shellfish poisoning (ASP), is an algal toxin produced naturally by some species of the diatom genus Pseudo-nitzschia. The toxin has been detected in a diverse array of marine organisms from copepods to whales. Cephalopods, which are important members of the food chain and active predators of known toxin vectors such as bivalves, crabs and some fishes, have just recently been implicated in DA transfer or accumulation. Here we present data showing detectable values of DA determined by HPLC-UV (high-performance liquid chromatography and ultraviolet detection) and confirmed by HPLC-MS (mass spectrometric detection) in two octopus species collected along the Portuguese continental coast: Eledone cirrhosa and E. moschata. Domoic acid was frequently detected in the digestive gland of E. moschata and occasionally reached concentrations exceeding 100 µg g−1. In contrast, E. cirrhosa contained lower concentrations of DA on the few occasions that it was detected. This suggests that E. moschata is a potential vector for DA transfer to higher trophic levels in the coastal marine food web, not excluding humans. These data, combined with known aspects of the life history of the species, are a necessary step towards achieving an understanding of the accumulation of phycotoxins in cephalopods.

Mediterranean demersal fisheries have experienced an ongoing decline in catches over the past 20 years as a result of excessive increases in effort caused both by growth in trawler engine power and by rapid technological advances in fish finding and fishing technology. This has led to an overexploitation of these resources. An increasing share of the catches consists of immature individuals. This study was undertaken to test a sorting grid with a bar spacing of 20 mm as a means of excluding juveniles in the commercial hake (Merluccius merluccius) fishery in the Catalan Sea, western Mediterranean. The grid was placed in the extension section of the gear 5 m in front of a cod-end. Divided cod-end design was used to collect the escapees and target species. The mean selection length (L50) of the ten hauls was 14.2 ± 0.7 cm SE, with a selection range of 7.3 cm ± 0.4 SE. The biomass of hake under L50 that escaped through the grid represented 50.1% ± 6.7 SE of the total hake biomass. These results are promising and indicate that a sorting grid can be used in excluding young hake. This was a first step toward implementation of sorting grids in commercial trawl gears as means of avoiding unwanted catches of small individuals in the hake fisheries in the Mediterranean Sea. Further trials are required to improve the sorting efficiency of the grid.

Monitoring the abundance of green turtles (Chelonia mydas) is necessary to assess population trends and risks of collapse. This note presents a study aimed at comparing three techniques for the direct estimation of green turtle numbers in their foraging habitats (seagrass beds and reef flats). The experiment was carried out at Mayotte Island, Western Indian Ocean. The techniques involved were surveys by snorkel, and aerial surveys using a microlight aircraft and a paramotor. Each technique had shortcomings and advantages. While each technique provided estimations of turtle numbers only surveys by snorkel permitted identification of species and sex, whenever visibility and turtle behaviour permitted. Along the shorelines, and over foraging areas, the paramotor was found to be most suitable for direct estimations of turtle numbers. The major advantage of this technique lied in its capability to obtain a synoptic snapshot of turtle distribution over foraging areas. Linear surveys from a microlight aircraft are better suited to monitor foraging areas located further away from the shore.

The Australian freshwater crayfish, Cherax destructor is cultured commercially and has been translocated throughout much of Australia. Previous investigation on C. destructor using 16S rRNA sequences of samples collected from natural environments has revealed a significant phylogeographic structure in this species with three well supported geographically non-overlapping clades, namely ‘northern’ C. d. destructor, ‘southern’ C. d. destructor and C. d. albidus. Movement of individuals beyond their natural range of distribution may have adverse effects on genetic integrity of the species. In the present study, aspects of translocations of the species were genetically investigated. Sequences of the 16S rRNA gene region of the mitochondrial DNA (mtDNA) were obtained from samples collected in nine quasi-natural waterbodies, supplemented with sequences of samples obtained from 31 natural waterbodies examined in a previous study. Results of phylogeographic analysis provide evidence that certain haplotypes from major clades of C. destructor have been translocated. The findings of this study have important implications for the conservation and management of genetic diversity within C. destructor.