The rapid development of the albacore tuna (Thunnus alalunga) driftnet fishery in the Bay of Biscay (Atlantic ocean, France) has incited European management authorities to ask for a study of its ecological impact on populations of common dolphins and striped dolphins. A programme with onboard observers has been led during 1992 and 1993, and a sighting survey has allowed the evaluation of the abundances of fractions of populations in the studied area. For the population of common dolphins, the biological parameter estimation has allowed the building of a discrete age-structured model based on a Leslie matrix. Sensitivity studies have been conducted using four model parameters (age of first reproduction, interval between births, juvenile and adult survival rates. Results show that the increase rate of the population presents the highest sensitivity versus adult survival rate and, in second place versus the interval between births.

Eggs from three distinct populations of walleye Stizostedion vitreum, one domesticated (London State Fish Hatchery) and two wild (Lake Erie and Salt Fork Reservoir), were compared in terms of total lipid content and fatty acid profiles (phospholipids and neutral lipids). The concentrations of total lipids in eggs from domesticated broodstock were significantly lower (8.6 ± 1.0 % of wet weight) than those of both wild populations (13.3 ± 0.9 % and 10.9 ± 0.6 % of wet weight for Lake Erie and Salt Fork Reservoir, respectively). The profiles of fatty acids in egg lipids differed significantly among the three investigated populations. Domesticated females fed a formulated diet produced eggs containing significantly higher levels of linoleic acid (18:2n-6), characteristic of plant lipids. However, arachidonic acid (20:4n-6), was at significantly higher levels in eggs of wild walleye stocks. Although eicosapentaenoic acid (20:5n-3) was detected at significantly higher levels in eggs from Lake Erie walleye, docosahexaenoic acid (22:6n-3), the most abundant in polar lipids, was found at similar levels in eggs of all three populations. Survival of walleye embryos was correlated with the concentrations of polyunsaturated long chain fatty acids. Our data suggest that deficiency in n-3 fatty acids might be associated with impaired development of walleye, and thus poor larval and juvenile viability.

The fatty acid profile of the galaxiid fish Galaxias maculatus (Salmoniformes) collected from an estuarine habitat (a river mouth), a freshwater creek and two land-locked freshwater lakes in Victoria, Australia, were investigated with a view to evaluating habitat influences on the fatty acid profile. Fish from the freshwater creek were unpigmented, fresh-run juveniles (referred to as whitebait), the others adult fish. The fatty acids that predominated in adult G. maculatus muscle were 16:0 and 22:6(n-3), and 16:0 and 18:1(n-9), respectively. In whitebait 22:6(n-3), 20:5(n-3) and 16:0 were predominant. Hopkins estuary fish had the highest amount of 18:2(n-6) but the lowest 18:3(n-3). In all galaxiid populations, polyunsaturated fatty acids (PUFA) were the main group of fatty acids in total lipid in muscle, and accounted for more than 40 %, followed by saturates and monoenes. In landlocked populations, the amount of monoenes was lower than in other galaxiid populations. G. maculatus whitebait had significantly lower amount of saturates and the highest amount of n-3 fatty acids. The ratio of n-3 to n-6 PUFA ranged from 4.6 (Hopkins estuary) to 7.6 (whitebait), and the former differed significantly from all the other populations. The main fatty acids predominating in the liver of galaxiids from landlocked (Lake Bullen Merri) and estuarine populations were 16:0, 22:6(n-3) and 18:1(n-9), and generally reflected the corresponding pattern in muscle. A principal component analysis of the fatty acid composition of muscle samples confirmed and highlighted the distinct fatty acid profile of the populations investigated, when three groupings could be discerned. The study suggests that in addition to the diet, other habitat related factors may influence the fatty acid profile in catadromous G. maculatus.

A sperm cryopreservation protocol adapted from turbot, was tested on sea bass using either 250-μL straws or 1.5-mL cryovials. A dilution to 1/3 in Mounib's extender and a cooling rate of −65 °C·min−1 allowed frozen sperm to recover an initial motility similar to that of fresh sperm at thawing; however, significant differences in motility (P < 0.001, n = 10 fish semen) were observed at further post-activation times, the motility decrease being faster in thawed sperm. At the experimental scale, triplicate inseminations of 2-mL aliquots (approximately 2 000 eggs) showed a significant fertility decay of thawed sperm compared to that of fresh sperm (P < 0.01, n = 12 fish semen) when a discriminating 35·103 spermatozoa to egg ratio was applied. When 70·103 and 200·103 spermatozoa per egg were provided in the same experimental conditions, no significant difference appeared between the fertilisation rates of fresh and thawed sperm. In order to validate the procedure for production or cryobank purpose, a scaled-up protocol was established. Two and 50 mL batches of eggs (approximately 2·103 and 50·103 eggs, respectively) were inseminated in triplicate using either fresh or thawed individual sperms of 5 males with 200·103 spermatozoa per egg. The mean fertility decreased by 23.5 % due to cryopreservation. This decline was explained by the loss of fertility of only one sperm, and only in large-volume conditions, probably due to the delay of use after thawing.

Self-feeding systems allow fish to freely express feeding activity. A simple rod at the water surface can act as a trigger and provide fish with a way of obtaining pellets from a feeder. Such a rod presented to experienced European seabass, Dicentrarchus labrax, may lead to feed wastage, probably as a result of unintentional fish contacts with the trigger. Trigger protection screens have been designed to prevent fish contacting the trigger by chance, and the efficacy of such screens was tested. Nocturnal and diurnal feed delivery and feed wasted were compared under conditions where the rod was unprotected or protected by semi-cylindrical or cylindrical screens. Tests were conducted using an unrestricted self-feeding regime (reward: 0.2 g pellet per kg of body weight and per fish contact) in juvenile seabass (57 g body weight) fed for 28 days at 21.3 °C. Fish were subjected to a 4-h L:20-h D (light:dark) photoperiod. The daily feed demand pattern and the nocturnal and diurnal feed wastage were recorded. Fish activated the trigger predominantly at night, except in the case of one group exposed to a trigger protected by a semi-cylindrical screen. in the latter, triggering activity was progressively distributed throughout the light:dark cycle. The cylindrical screens markedly reduced feed wastage and seabass were able to locate and activate the trigger (even in total darkness) to obtain a reward.

The reproductive performance of pond tiger shrimp given astaxanthin (100 mg·kg−1) and/or vitamin A (20 000 IU·kg−1) for 61 d in tanks was assessed in a 2 × 2 factorial experiment in a completely randomized design. Tissue carotenoid (total carotenoid; astaxanthin free form. AF; monoester, AM; diester, AD) was analyzed using high performance liquid chromatography. The gonad index (GI) of shrimps fed diets with astaxanthin and/or vitamin A (3.05 ± 0.11 to 3.30 ± 0.17) were significantly higher than shrimps not fed any supplement (2.24 ± 0.17). A significant interaction between astaxanthin and vitamin A for ovarian development and spawning was detected (GI, 3.18 ± 0.14). The ovarian total carotenoid (10.85 ± 1.52 μg·g−1) and astaxanthin (AF, 7.65 ± 1.43 μg·g−1; AM, 0.63 ± 0.12 μg·g−1) content of shrimps fed a diet with astaxanthin supplement were significantly higher than those without. In shrimps fed diets with and without vitamin A, no differences in ovarian total carotenoid (9.38 ± 0.58 μg·g−1) and AF (8.12 ± 1.55 μg·g−1) content were observed except for AM (0.64 pm 0.15 μg·g−1) content. In contrast, the ovarian AD level was significantly higher (1.14 ± 0.3 μg·g−1) in shrimps fed diets with both supplements compared to other diets. A significant interaction between astaxanthin and vitamin A was detected for AD storage. In the hepatopancreas of shrimps fed diets with or without astaxanthin or vitamin A, no significant differences in AF and AM content was observed. On the other hand, the AD (4.92 ± 1.3 μg·g−1) level in the hepatopancreas of shrimps fed diet with vitamin A was significantly higher than those without. These results suggest the involvement of astaxanthin in P. monodon reproduction and its need for inclusion in broodstock diets. Supplementation of vitamin A to broodstock diet of P. monodon appears to enhance its ovarian development and spawning.