Larval fish assemblages in nearshore waters of southeast Gulf of California: vertical and temporal patterns

The influence of salinity and temperature on larval fish assemblages, as well as, temporal and vertical patterns on larval fish assemblages off the inlet of the Presidio River, southeast coast of the Gulf of California were evaluated. Samplings for ichthyoplankton and environmental parameter measurements were carried out at three depths, in five sampling sites, during September and December 1994, and April and June 1995. Anchovies and herrings (Clupeiformes) were the most abundant larval fish accounting for 77% of the total abundance. A significant relationship between salinity and the abundance of larval herrings (Opisthonema medirastre and O. dovii) and between the water temperature and the abundance of the weakfish (Cynoscion reticulatus) was found. Anchovies (Anchoa lucida, A. walkeri, and A. nasus) were present in all sampled months, while O. medirastre and O. dovii occurred in December and June, and C. reticulatus in September. Larvae of pelagic fish were more abundant near the surface, while larvae of demersal fish were more abundant near the bottom. The present study, by emphasising the importance of considering temporal and vertical changes in larval fish assemblages in coastal environments with ecological and economic importance, will be useful for designing more efficient sampling programs.(AU)

Se evaluó la influencia de la salinidad y la temperatura, así como patrones temporales y verticales en la comunidad de larvas de peces enfrente del río Presidio, costa sudeste del Golfo de California. Los muestreos de ictioplancton y las mediciones de los parámetros ambientales fueron realizados a tres profundidades, en cinco sitios de muestreo, durante septiembre y diciembre de 1994, y abril y junio de 1995. Las anchoas y sardinas (Clupeiformes) fueron las larvas de peces más abundantes representando el 77% de la abundancia total. Se encontró una relación significativa entre la salinidad y la abundancia de larvas de sardinas (Opisthonema medirastre and O. dovii), y entre la temperatura del agua y la abundancia de la corvina rayada (Cynoscion reticulatus). Las anchoas (Anchoa lucida, A. walkeri y A. nasus) estuvieron presentes en todos los meses muestreados, mientras que O. medirastre y O. dovii ocurrieron en diciembre y junio, y C. reticulatus en septiembre. Las larvas de peces pelágicos fueron más abundantes cerca de la superficie, mientras que las larvas de peces demersales fueron más abundantes cerca del fondo. El presente estudio, al enfatizar la importancia de considerar los cambios temporales y verticales en el ensamblaje de larvas de peces en ambientes costeros con importancia ecológica y económica, será útil para diseñar programas de muestreo más eficientes.(AU)

Comparison of some reproductive characteristics of farmed and wild white shrimp males Litopenaeus vannamei (Decapoda: Penaeidae)

We rated some reproductive characteristics of white shrimp Litopenaeus vannamei (Boone, 1931) males using 46 farmed individuals (weighing 21.42 +/- 0.56 g) and 40 wild individuals (weighing 36.10 +/- 0.72 g). In farmed shrimps, spermatophore mean weight was 8.94 +/- 0.51 mg; total mean sperm count was 3.90 +/- 0.27 x 10(6) in each spermatophore; and mean percentage of normal sperm was 86.9 +/- 0.37%. In wild individuals, the respective values were 30.68 +/- 2.32 mg; 6.22 +/- 1.09 x 10(6); and 62.1 +/- 3.56%. In both groups, the differences between right and left spermatophore were not significant (p < 0.01). There were significant differences in spermatophore weight and percentage of normal sperm between farmed and wild shrimps; sperm counts differences, however, were not significant (p < 0.01). The relationship between spermatophore weight (Ws) and individual weight (Wo) was Ws (mg)=1.23 (Wo)-17.34 (r2=0.89), in farmed shrimps; and Ws (mg) = 2.57 (Wo)-60.04 (r2 = 0.64), in wild ones. In cultivated organisms, the relationship between sperm counts (Cs) and individual weight (Wo) was Cs (x 10(6)) = 1.13 * 10(-4*) (Wo) 3.361 (r2 = 0.85); and versus spermatophores weight was Cs (x 10(6)) = 0.439* (Ws) 0.984 (r2 = 0.90). In wild organisms, there was no correlation. The proportion of normal sperm ranged from 79.8 to 95.2 % (86.9 +/- 0.37%) and from 14.0 to 91.5% (62.1 +/- 2.52%), in farmed and wild shrimps, respectively. The most frequent abnormalities in both farm and wild animals were sperm without spike (49.3% and 76.6%, respectively) and irregular shape (35.8 % and 17.7 %). The less frequent occurrences were those of bent (10.2 % and 4.29%) and double spike (4.7% and 1.41%).

Comparison of some reproductive characteristics of farmed and wild white shrimp males Litopenaeus vannamei (Decapoda: Penaeidae).

We rated some reproductive characteristics of white shrimp Litopenaeus vannamei (Boone, 1931) males using 46 farmed individuals (weighing 21.42 +/- 0.56 g) and 40 wild individuals (weighing 36.10 +/- 0.72 g). In farmed shrimps, spermatophore mean weight was 8.94 +/- 0.51 mg; total mean sperm count was 3.90 +/- 0.27 x 10(6) in each spermatophore; and mean percentage of normal sperm was 86.9 +/- 0.37%. In wild individuals, the respective values were 30.68 +/- 2.32 mg; 6.22 +/- 1.09 x 10(6); and 62.1 +/- 3.56%. In both groups, the differences between right and left spermatophore were not significant (p < 0.01). There were significant differences in spermatophore weight and percentage of normal sperm between farmed and wild shrimps; sperm counts differences, however, were not significant (p < 0.01). The relationship between spermatophore weight (Ws) and individual weight (Wo) was Ws (mg)=1.23 (Wo)-17.34 (r2=0.89), in farmed shrimps; and Ws (mg) = 2.57 (Wo)-60.04 (r2 = 0.64), in wild ones. In cultivated organisms, the relationship between sperm counts (Cs) and individual weight (Wo) was Cs (x 10(6)) = 1.13 * 10(-4*) (Wo) 3.361 (r2 = 0.85); and versus spermatophores weight was Cs (x 10(6)) = 0.439* (Ws) 0.984 (r2 = 0.90). In wild organisms, there was no correlation. The proportion of normal sperm ranged from 79.8 to 95.2 % (86.9 +/- 0.37%) and from 14.0 to 91.5% (62.1 +/- 2.52%), in farmed and wild shrimps, respectively. The most frequent abnormalities in both farm and wild animals were sperm without spike (49.3% and 76.6%, respectively) and irregular shape (35.8 % and 17.7 %). The less frequent occurrences were those of bent (10.2 % and 4.29%) and double spike (4.7% and 1.41%).