A statistical approach is proposed to utilize the information contained both in scientific surveys and commercial fishing logbooks, in order to determine spatial and temporal distributions of recruiting and spawning fish of exploited populations. The approach is based on multivariate descriptive methods including ordination methods and classification techniques. A typology involving a principal component analysis (PCA), followed by a hierarchical ascending classification (HAC), is applied to both scientific and commercial data. PCA that accounts for spatial and temporal contiguities were performed. These analyses allow to compare structures observed at global and local scales, with those observed without focusing on a particular scale. The method is applied to the whiting population in the Celtic Sea. The analyses performed on both scientific and commercial CPUE show that most age groups are found north of 50°N. The analysis of commercial CPUE indicates four periods in the year associated with particular areas. High abundances of adults (age >2 years) are observed during spawning season (January–April) in inshore areas (south of Ireland and off Cornwall). Intermediate abundances of adults are observed in the same area in May and June. Between July and September, all age groups are observed in the Smalls area, where particularly high abundance of recruiting group 1 are found. During the last quarter, the distribution of adults is more widespread, mainly ranging between 51°N and 52°N.

Monthly variations in spatial and depth distributions, sex ratios, and maturity status in two species of hakes, Merluccius hubbsi and M. australis, were analysed in an area where their ranges overlap spatially on the shelf and slope around the Falkland Islands, and in international waters at 45–47° S (High Seas), using data collected by scientific observers on commercial fishing vessels. A variety of exploratory analyses were carried out on the raw data before patterns were quantified using generalised additive models. Both species use the areas studied as their feeding grounds. M. australis occur mainly on the Falkland shelf south of 51° S, whereas M. hubbsi is widely distributed throughout both the Falkland and High Seas shelf areas. Preliminary schemes of the seasonal migrations of both hakes in Falkland waters and on the High Seas are suggested and discussed. M. hubbsi and M. australis are found to be boldly segregated, both spatially and temporally, on their common feeding grounds, thus avoiding potential inter-specific competition for food resources.

The Latin American shrimp Litopenaeus stylirostris was introduced in three different Pacific islands (Tahiti, New Caledonia via Tahiti, and Hawaii) and hatchery-propagated for 7–25 generations to develop shrimp farming based on these domesticated stocks. Three microsatellite markers have been used in an attempt to assess the genetic bases of the populations available to start a selective breeding program. The comparison of eight hatchery stocks (five New Caledonian, two Hawaiian and one Tahitian stocks) and one wild Ecuadorian population showed a much lower variability in the domesticated stocks than in the wild population, especially in New Caledonia and Tahiti (2–3.7 vs. 14–27 alleles per locus; 20–60% vs. 90% expected heterozygosity). The Tahitian and the New Caledonian stocks share the same alleles, suggesting that the loss of alleles occurred during the common past of these populations. On the contrary, New Caledonian and Hawaiian populations share only one common allele at the three loci studied. Although the low genetic variability and the resulting inbreeding of the New Caledonian stocks do not seem to affect their present performance, the results of this study demonstrate the usefulness of the introduction of new stocks in order to increase the potential responses to new controlled or uncontrolled selective pressures. The introduction in New Caledonia of the Hawaiian domesticated stocks, which would provide the local shrimp industry with 40% of the allelic diversity of the species, is advised and preferred to the one of wild animals in order to take advantage (i) of the spontaneous selection which occurred during domestication and (ii) of their favourable sanitary "specific pathogen free" status (no presence of four viruses: WSV, YHV, IHHNV, TSV) which limits the risk of introduction of pathogens.

The chronic effects of exposing sea bass (average initial weight 100 g) to ammonia in water at 22 °C were first evaluated over a 61-day period (period 1, P1) during which nine different groups were submitted to nine ambient ammonia levels ranging from 0.014 to 0.493 mg l–1 NH3-N (0.53–16.11 mg l–1 total ammonia nitrogen (TA-N)) and fed using self-feeders. At the end of P1, the fish were starved for 10 days (P2). Their recovery capacity was tested over 43 days (P3) after which the exogenous ammonia supply was stopped in all treatments and the fish were allowed to feed. After 20 days of exposure a highly significant effect of ammonia was evident from the decrease in feeding activity, voluntary feed intake (VFI) and specific growth rate (SGR), and the increase in the feed conversion ratio (FCR). Ammonia exposure had no effect on circadian feeding rhythm or hourly actuation profiles. At the end of P1, the fish seemed to have adapted to all ambient ammonia concentrations tested since feeding and growth parameters were independent of ammonia levels. But they were unable to compensate for growth losses. Physiological adjustments were observed: plasma TA-N concentrations were positively related to ambient TA-N while there was no major disturbance in plasma urea. Plasma tri-iodo-thyronine concentrations were affected by ambient ammonia concentrations and there were no significant changes in hydromineral balance. During P2, oxygen consumption and urea excretion did appear to have been affected by ambient ammonia. When the exogenous supply of ammonia was stopped (P3), fish exhibited hyperphagia and compensatory growth. In fish previously exposed to the highest ammonia levels, SGR and VFI were highest, and their FCR was improved. At the end of the experiment the final average weights were similar in all of the treatments (range 337–396 g). Depending on the concentrations used, ammonia exposure may enhance subsequent fish appetite and growth rate and have a similar effect on growth performances as restricting feeding level. Within the range tested, no detrimental effect of ammonia on the metabolic capacity of the fish, measured by oxygen consumption and urea excretion, or on their physiological status was recorded, and the fish had a good recovery capacity. In the conditions of the experiment, the non-observable effect concentration (NOEC) was 6 mg l–1.

Several molluscs that have been introduced world-wide have become economically important for coastal communities. As far as it is known, at least four scallop species (Argopecten irradians, Argopecten purpuratus, Patinopecten yessoensis, Pecten maximus) have been moved between different biological provinces and it is possible there will be further such movements. Making an introduction involves responsibilities and so requires careful consideration. This is because there have been several unwanted impacts with movements of molluscs in the past. The International Council for the Exploration of the Sea's (ICES) 1995 Code of Practice on the Introductions and Transfers of Marine Organisms and recent revision provides a basis for undertaking such an action wisely. In this review, scallops that may be used in future cultivation or in fisheries as potential candidates are examined in relation to the first phase of an introduction—the prospectus. This prospectus should take account of the purposes and objectives of the introduction, including relevant biological, pathological and ecological conditions in the donor region and the potential impacts of the species in the expected range occupied in the recipient region. This may require a study visit to the donor region to evaluate concerns relating to potential hazards. The ecomorphology of five different scallop shell morphs is discussed in relation to their behaviour and occupied habitat. Such information may provide an indication of their interaction with native scallop species in advance of their introduction.

Although fish have been kept for more than three centuries as ornamentals, and the development of manufactured feed since 50 years ago has contributed to the tremendous growth of this hobby, nutrition of ornamental fish is based on extrapolation of results derived from food fishes under intensive farming conditions. Some research on nutrient (protein, minerals) requirements of growing freshwater ornamental species (live-bearers) in a production environment has been conducted, mainly in Singapore, with emphasis on the provision of live feed during the early stages of the life cycle. Protein requirements varied from around 30% dietary protein for growing omnivorous goldfish (Carassius auratus) to 50% for the carnivorous discus (Symphysodon aequifasciata). Whereas mineral (phosphorus, iron, magnesium, zinc) requirements have received some attention in the guppy (Poecilia reticulata), few researches have concentrated on vitamin requirements of ornamental species. Requirements for fatty acids have been conducted mainly on marine ornamentals (damselfish, seahorses), and accentuated the need for dietary supplementation of n-3 highly unsaturated fatty acids. Fish kept in public and home aquaria presents the problem of diversity of species in the same enclosure, each with its own specific requirements and needs. Maintenance energy levels of ornamental fish varied from 0.068 kJ per day for small neon tetras (Paracheirodon innesi) to 0.51 kJ per day for moonlight gouramis (Trichogaster microlepsis) kept at a water temperature of 26 °C. Research on nutrient requirements of ornamental fish urges for suitable measurements other than only growth rate in order to determine optimal dietary inclusion levels.

Echosounder data from four surveys (1992, 1993, 1995 and 1996) is used to investigate the spatio-temporal variability of school behaviour in North-Western Mediterranean waters. The schools are described using morphological, energetic, spatial and temporal descriptors. The variability in the morphological, positional and energetic parameters of the schools is attributable more to the size of the school's individuals (juveniles or adults) than to the relative composition (percentage) of pelagic species in the area. This fact made difficult the identification of species in the studied area. The concentration of schools in certain geographic zones is determined by local oceanographic characteristics that favour the trophic or reproductive activity of these species. The diurnal aggregative behaviour of pelagic species is typical of the zone and no schools were detected at night. The biomass of the pelagic species in the area under consideration has diminished during the 4-year study period and no relationship was found between the number of schools and the biomass evaluated. This is the first time that the schools of small pelagic fishes from the Spanish Mediterranean Sea have been described and the information could be useful to the management and exploitation of the fisheries in the area.