A longline ‘métier’ using small hooks for ‘red’ sea breams (Pagellus acarne and Pagellus erythrinus) in the Algarve (south of Portugal) was studied. Experimental longlining was carried out with three sizes of "Mustad" round bend, flatted, spade end Quality 2316 DT hooks (numbers 11, 13 and 15) and two types of bait: razor shell (Ensis siliqua) and mud shrimp (Upogebia pusilla). A total of 3 328 fish and at least 36 species were caught with 33 600 hooks fished in 28 longline sets. Five species of sea breams (Sparidae) accounted for 79% of the catch: Pagellus acarne, Pagellus erythrinus, Diplodus vulgaris, Spondyliosoma cantharus, and Boops boops. High catch rates of 20-30 fish per 100 hooks were made in a number of 1 200 hook longline sets, with total catch weights of 40 to more than 60 kg per set. In general, the smallest hook (number 15) had the highest catch rate. Bait type did not significantly affect the catch size distributions. Although more fish were caught with the razor shell bait, higher catch rates of ‘red’ sea breams were obtained with mud shrimp. Catch rates were also affected by the location of the fishing grounds and the time of the set, with the highest catch rates obtained when the longline was set within two hours before sunrise. A wide size range was caught for each species, with highly overlapped catch size frequency distributions for the three hook sizes used. Except for Spondyliosoma cantharus, few illegal-sized fish were caught, even with the smallest hook. The logistic model fitted by maximum likelihood was used to describe hook selectivity for Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, and Spondyliosoma cantharus.

In order to manage the fish stock of the Senegal coastal zone it is necessary to carry out direct assessment surveys by acoustic methods. Acoustic surveys were carried out in this region from a sports-fishing boat, using a split-beam echo sounder in vertical mode, in areas with depth less than 15 m. On a short time scale, spatial structure of the fish population remained stable. The average acoustic biomass detected was variable, but we observed a relative stability of target strength distribution of single fish. The use of acoustic methods in these areas of shallow depths, the consequences of escape behaviour of the fish, and sampling strategies are discussed.

Brown trout and rainbow trout (average weight 100 g) were reared in fresh water at 12 °C under the same conditions before transferring brown trout to sea water, in order to compare phosphorus utilisation in both species. Apparent phosphorus availability, orthophosphate excretion and phosphorus accretion in the fish were directly determined. Thus, actual phosphorus mass balance was built. Rainbow trout raised in fresh water had a higher phosphorus retention coefficient (maximum 50 %) than brown trout reared in fresh water (maximum 45 %). Transferring brown trout to sea water induced a reduction in phosphorus retention (maximum 39 %). Orthophosphate excretion, ranging 7-20 mg phosphorus per kg wet weight per day, represented 10-20 % of ingested phosphorus. Phosphorus availability was lower in brown trout raised in sea water (65 %) than brown trout raised in fresh water (76 %). Phosphorus balance measurements showed that 90 to 98 % of phosphorus flow could be accounted for.

Zero-water exchange culture tanks were stocked with Penaeus vannamei postlarvae to compare the effects of (i) three dietary phosphorus levels: 0.4, 0.8 and 1.2 %, and (ii) three dietary inorganic phosphorus sources: CaHPO4, Na2HPO4 and NaH2PO4, on postlarvae biological performance, and total reactive phosphorus accumulation in the water (TRPAW). Dietary Ca:P ratio was maintained within a 1:1 to 1:2 ratio. Postlarvae survival was high and not significantly different among treatments. Postlarvae growth was not significantly different, regardless of dietary phosphorus level. TRPAW was significantly higher with increasing level of dietary phosphorus. Dietary inorganic phosphorus source did not have a significant effect on postlarvae growth. No significant differences were found on TRPAW between diets with Na2HPO4 and NaH2PO4 supplementation at equal dietary phosphorus level. TRPAW was significantly lower with CaHPO4 than with Na2HPO4 or NaH2PO4 supplementation at equal dietary phosphorus level. Environmental quality of culture water may be greatly modified through nutritional strategies without negatively affecting shrimp biological performance.

The effects of toxic and non-toxic strains of Alexandrium sp. on the initial feeding responses of the Pacific oyster Crassostrea gigas were determined by continuous monitoring of the clearance rate of individual oysters. This was determined fluorometrically by loss of fluorescence of live microalgae introduced as food. Feeding oysters with toxic or non-toxic A. tamarense and toxic A. fundyense resulted in stop/start clearance behaviour. In contrast, control oysters fed a reference microalga, Isochrysis sp., known to support their growth, did not exhibit this behavior. Pacific oysters acclimated to Isochrysis sp., fed mixtures of Alexandrium/Isochrysis, showed further evidence of stop/start clearance. Exposure for periods up to 48 hours with non-toxic A. tamarense did not enhance clearance of either Alexandrium or Isochrysis.

The survival of turbot eggs and the rearing capacities of larvae stemmed from artificial fertilization practices using frozen-thawed spermatozoa were evaluated. Furthermore, the viability of sperm samples stored during a 9 month period in liquid nitrogen was assessed. No significant difference in the fertilization rate, hatching rate, survival and wet weight of 10-day old larvae were observed using fresh or frozen-thawed spermatozoa. The motility recorded at 10 s and 60 s post-activation and the fertilization capacity of frozen-thawed spermatozoa were not significantly decreased during a 9 month storage period in liquid nitrogen. These results confirm the high quality of the turbot spermatozoa stemmed from the cryopreservation process, allowing their use for routine aquaculture practices.