The Panama grunt is an abundant and commercially important species in the southeastern Gulf of California, but the research undertaken on this species is scarce despite its ecological and economic importance. We studied the feeding habits of Panama grunt through stomach content analyses as a first step towards understanding the biology of this species in the study area. Our results indicate that the Panama grunt is a benthic predator throughout its life cycle and feeds mainly on infaunal crustaceans. Diet differences among grunt were not found according to size, diet, or season. Shannon diversity index results indicate that Panama grunt has a limited trophic niche breadth with a diet dominated by a limited number of taxa as crustaceans. The estimated trophic level of this species is 3.59. Overall, the Panama grunt is a carnivorous fish occupying the intermediate levels of the trophic pyramid.
Samples taken during the closed fishing seasons from 1992 to 2010 were analyzed at sea. These data along with the landing records for the fishing periods from 1992-1993 to 2009-2010 were used to allow the situation of Litopenaeus van-namei from the coasts of Sinaloa and Nayarit to be analyzed by means of stochastic models and by a graphic approach for the surplus biomass. Using the catch from 1993-1994 as a reference point and comparing this to the 2008-2009 catch revealed a stock decrease of about 65%. By taking into account the percentage contribution to total shrimp land-ings, these changes showed a decrease from 76% to 12%. There were changes between 2000 and 2001 when the fleet grew by 50%. Considering a 3600 t maximum sustained yield (MSY) in the series 1992-2010, 50% of the reports are lower. It is necessary to recover the stock
A population analysis was made using data of the grunt Pomadasys panamensis. The information is from the catch from 260 hauls in estuarine waters, open-ocean waters, and off the coast of Sinaloa and northern Nayarit, Mexico, in the southeastern Gulf of California. The area of influence is about 120,000 km2 and includes about a third of the drag area of the largest shrimp fleet of the American Pacific. The average length in the population was 210 mm. The maximum length was 430 mm and the minimum was 50 mm. The analysis for the frequency distributions of the lengths and the multinomial solution produced representative modal groups for 160 mm, 190 mm, and 230 mm. The simulation of the biomass density gave an estimate close to 90 t, with 650,000 organisms before starting the fishing season in the region. The density was 0.19 kg ha–1. The colonization was 0.42% or 42 %. The model was validated using the Aikaikae criterion (AIC). The results provide an overview of the initial biomass densities and population structure of the species caught as bycatch, demonstrating the importance of this species abundance in the shrimp fishery, and generating a source of monetary income to the crew of the fishing fleet. The persistence of the species to fishing provides an example to study the mechanisms of survival
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.
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