No abstract

No abstract

Prospectos de un colapso inducido por pesca en la carpa asiática del Río Illinois RESUMEN: . La carpa asiática amenaza con invadir el Lago Michigan a través del sistema de vías acuáticas del área de Chicago, lo cual podría acarrear serias consecuencias en las tramas tróficas de los grandes lagos. Además de los esfuerzos llevados a cabo para impedir el ingreso de estos peces al Lago Michigan mediante barreras eléctricas, el estado de Illinois ha iniciado un programa de pesca en el Río Illinois, cuya finalidad es reducir la densidad poblacional a través de una pesca comercial intensiva. En este estudio se exploran los prospectos de un colapso de la carpa asiática por medio de un régimen de pesca intensiva. Sobre la base de un meta-análisis de datos demográfi-cos, se desarrolla un modelo de simulación dinámica para comparar el desempeño de estrategias de explotación tanto reales como alternativas para el Río Illinois. Las proyecciones del modelo sugieren que, de mantenerse las tasas de captura por debajo de 0.7 o si la pesca continua siendo selectiva a tallas (dirigiéndose a peces >500 mm o <500 mm) o a especies (carpa cabezona), entonces es poco probable colapsar la carpa asiática en el Río Illinois, aunque la biomasa se puede reducir considerablemente. Se argumenta que, pese a lo anterior, es posible lograr el nivel de esfuerzo pesquero predicho por el modelo, necesario para colapsar las poblaciones de la carpa asiática, si la pesca comercial se expande y se combina con incentivos económicos con tal de mejorar la selectividad a la talla y a las especies objetivo. ABSTRACT: Invasive Asian Carp are threatening to enter Lake Michigan through the Chicago Area Waterway System, with potentially serious consequences for Great Lakes food webs. Alongside efforts to keep these fishes from entering LakeMichigan with electric barriers, the state of Illinois initiated a fishing program aimed at reducing their densities through intensive commercial exploitation on the Illinois River. In this study, we explore prospects for the "collapse" of Asian Carp in the Illinois River through intensive fishing. Based on a meta-analysis of demographic data, we developed a dynamic simulation model to compare the performance of existing and alternative removal strategies for the Illinois River. Our model projections suggest that Asian Carp in the Illinois River are unlikely to collapse if existing harvest rates are kept below 0.7 or fishing continues to be size selective (targeting only fish >500 mm or <500 mm) or species selective (targeting mostly Bighead Carp), although their biomasses could be greatly reduced. We argue that it would still be possible to achieve fishing effort targets predicted by our model to collapse the Asian Carp populations if efforts to expand commercial fishing are combined with economic incentives to improve size selectivity and species targeting.

No abstract

Routine metabolism (i.e. standard metabolism plus a low level of activity) of coastal largemouth bass Micropterus salmoides from Mobile-Tensaw Delta, AL, U.S.A. was examined as a function of temperature (15, 20, 25 and 30° C), salinity (0, 4, 8 and 12) and body mass (range 24-886 g) using flow-through respirometry. Functionally, a cubic relationship best described the effect of salinity on respiration; the magnitude of these effects increased with temperature and body mass. The best model predicted that specific respiration (mg O(2) g(-1) h(-1)) at temperatures >20° C was lowest at salinities of 0·0 and 9·7, and elevated at 3·2 and 12·0; salinity had little to no effect at temperatures ≤20° C. Respiration increased exponentially with temperature, but when compared with previously published respiration rates for M. salmoides from northern latitudes, predicted respiration was higher at cool temperatures and lower at high temperatures. The reduced energetic cost near the isosmotic level (i.e. c. 9) may be an adaptive mechanism to tolerate periods of moderate salinity levels and may help explain why M. salmoides do not flee an area in response to increased salinity. Further, these results suggest that salinity has high energetic costs for coastal populations of M. salmoides and may contribute to the observed slow growth and small maximum size within coastal systems relative to inland freshwater populations.