Ictioplancton en el estuario del río Pánuco, Tamaulipas-Veracruz

Se determinó la variación en la estructura del ensamblaje delarvas de peces a lo largo de un gradiente salino en el estuario del ríoPánuco, para lo cual se realizaron muestreos en: enero, marzo, mayo, julio,septiembre y noviembre en 2017 en nueve sitios, con una red estándar conabertura de malla de 500 μm. Se recolectaron 1 165 huevos de peces y526 larvas de peces de 18 especies, tres de ellas de agua dulce. La mayorriqueza de especies se observó en el estuario medio y laguna de PuebloViejo. Los valores mayores de diversidad y equidad se presentaron ennoviembre (2.7 y 0.9, respectivamente). La dominancia fue mayor en julio(0.4) debido a la abundancia de Anchoa mitchilli. El ensamblaje ictioplanctónicose caracterizó por un mayor número de especies dominantes marinasy estuarinas, un bajo número de dulceacuícolas y disminución de la riquezarío arriba.

Spatial ecology and growth in early life stages of bay anchovy Anchoa mitchilli in Chesapeake Bay (USA)

The bay anchovy Anchoa mitchilli is the most abundant fish in Chesapeake Bay (USA) and is a vital link between plankton and piscivores within the trophic structure of this large estuarine ecosystem. Baywide distributions and abundances of bay anchovy eggs and larvae, and larval growth, were analyzed in a 5 yr program to evaluate temporal and spatial variability based on research surveys in the 1995-1999 spawning seasons. Effects of environmental variability and abundance of zooplankton that serve as prey for larval bay anchovy were analyzed. In the years of these surveys, 97.6% of eggs and 98.8% of larvae occurred in the polyhaline lower bay. Median egg and larval abundances differed more than 10-fold for surveys conducted in the 5 yr and were highest in the lower bay. Within years, median larval abundance (ind. m-2) in the lower bay was generally 1-2 orders of magnitude higher than upper-bay abundance. Salinity, temperature, and dissolved oxygen explained 12% of the spatial and temporal variability in egg abundances and accounted for 27% of the variability in larval abundances. The mean, baywide growth rate for larvae over the 5 yr period was 0.75 ± 0.01 mm d-1, and was best explained by zooplankton concentration and feeding incidence. Among years, mean growth rates ranged from 0.68 (in 1999) to 0.81 (in 1998) mm d-1 and were fastest in the upper bay. We identified environmental factors, especially salinity, that contributed to broadscale variability in egg and larval production.

Estructura de la comunidad de peces en el sistema Candelaria-Panlau, Campeche, México

Se describe el comportamiento de los parámetros de temperatura, salinidad, transparencia del agua y temperatura ambiente, y de la abundancia y diversidad de la comunidad del peces del sistema Candelaria-Panlau en escalas temporal y espacial. Los trabajos de campo se realizaron de manera mensual en cinco estaciones entre abril de 1993 Y abril de 1994. La comunidad de peces quedó representada por 50 especies con 7 926 organismos y 144.7 kg de peso. Los valores de abundancia y diversidad de la comunidad fueron: 0.09 ind/m2, 1.61 g/m2 18.25 g/ind, H'n = 1.879, J = 0.475 Y D = 5.681. Las especies con dominio ecológico fueron: Cathorops melanopus, Diapterus rhombeus, Anchoa mitchilli, Sphoeroides testudineus, Bairdiella chrysura, B. ronchus, Cynoscion arenarius, y C. nebulosus, que en conjunto representan el 90.9 % en número y el 78.9 % en peso de la captura total. Las matrices de valores de los parámetros ambientales y de abundancia numérica de la comunidad de peces, fueron sometidas a un análisis de factores con el método dé extracción de componentes principales, su representación gráfica confmna la definición de especies dominantes y demuestra que la salinidad, estación cinco y mes de febrero son los componentes que caracterizan al sistema y a la comunidad de peces.

Side-aspect target-strength measurements of bay anchovy (Anchoa mitchilli) and Gulf menhaden (Brevoortia patronus) derived from ex situ experiments

Boswell, K. M., and Wilson, C. A. 2008. Side-aspect target strength measurements of bay anchovy (Anchoa mitchilli) and Gulf menhaden (Brevoortia patronus) derived from ex situ experiments. – ICES Journal of Marine Science, 65: 1012–1020. Acoustic target strengths (TSs) of bay anchovy [Anchoa mitchilli, 4.7–6.1 cm TL (total length)] and Gulf menhaden (Brevoortia patronus, 5.1–7.7 cm TL) were measured at 420 kHz during side-aspect, ex situ experiments. TS–TL relationships were derived at aspect for tethered individuals, and TS distributions were compared with those of free-swimming fish. Linear models relating TS and TL were fitted to data at two levels of pulse duration (0.1 and 0.4 ms) for both side aspect and all horizontal aspects of each species, and for pooled data from both species. At a pulse duration of 0.4 ms, the side-aspect TS–TL relationships were anchovy: TSlateral = 19.5 log10 TLcm − 62.4; menhaden: TSlateral = 26.1 log10 Lcm − 65.6; pooled: TSlateral = 32 log10 TLcm − 70.9. For all horizontal-aspect orientations (0–180° in the horizontal) the best-fit TS–TL relationships were anchovy: TSall = 20 log10 TLcm− 65.4; menhaden: TSall = 20 log10 TLcm − 64.8; pooled: TSall = 20 log10 TLcm− 65. However, the “fit” for all angles was consistently low. Predicted TS comparisons with side-aspect models presented by earlier authors suggested biases in the estimated TL. Additionally, relationships between TS and wet weight (W) were derived for each species. Variation in TS by pulse-duration level suggests the potential for the use of this factor as a time-dependent variable by which to separate echoes from bay anchovy and Gulf menhaden.