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Surface sediment samples collected from the Salina Cruz Bay in the last twenty years, were analyzed for the total available trace elements (Cr, Cu, Fe, Pb, Ni, V, and Zn) to evaluate metal contamination due to possible anthropogenic inputs. Normalization of metals to iron and fine-grained fraction (< 63 microm) indicated relatively high enrichment factors for lead during the last two decades. Sediment Quality Guidelines suggest that lead must be considered as a chemical of potential concern in the marine and estuarine ecosystem. Concentration levels of lead ranged from 5-124 microg/g, while Ni and V below 70 and 30 microg/g, respectively. Geoaccumulation and enrichment factors for the rest of elements show comparable values to those reported for sites with similar activities in the world. Spatial distribution suggests that in addition to harbor activities, a transboundary source for Pb must account for the observed trends.

Bycatch fish species from shrimp industrial fishery in the Gulf of California, Mexico. The shrimp fishery in the Gulf of California is one the most important activities of revenue and employment for communities. Nevertheless, this fishery has also created a large bycatch problem, principally fish. To asses this issue, a group of observers were placed on board the industrial shrimp fleet and evaluated the Eastern side of the Gulf during 2004 and 2005. Studies consisted on 20kg samples of the capture for each trawl, and made possible a systematic list of species for this geographic area. Fish represented 70% of the capture. A total of 51 101 fish were collected, belonging to two classes, 20 orders, 65 families, 127 genera, and 241 species. The order Perciformes was the most diverse with 31 families, 78 genera, and 158 species. The best represented families by number of species were: Sciaenidae (34) and Paralichthyidae (18) and Haemulidae and Carangidae (16 each). The best represented genera in number of species were Symphurus (nine) and Diplectrum and Cynoscion (six); other important genera were Larimus and Porichthys with five species each. The best represented species in number were Syacium ovale,

Taxonomic composition and zoogeographic relations of demersal in the western coast of Baja California Sur, Mexico. The composition of demersal fish along the western coast of the State of Baja California Sur, México, including the limit of the northern distribution of the ichthyofauna of the eastern tropical Pacific, is presented. The survey was carried out on four oceanographic cruises between autumn 2004 and March 2006. Of 220 species in 132 genera and 73 families, 26.3% are species of wide distribution from San Diego County, USA to Panama and 21.7% are species restricted to the eastern tropical Pacific. Six species are new findings for the area or range expansions. The families with the most species are Paralichthyidae and Scorpaenidae, each with 16 species. The most frequent genus was Sebastes, with nine species. We present a table with common Spanish names, size range and status of each species inside the community.

A bioeconomic approach was used to evaluate random variation of growth and mortality parameters and feed conversion ratio (FCR) for intensive production of the blue shrimp Litopenaeus stylirostris (Stimpson). Severe mortality problems caused by high impact diseases were not considered in this analysis. For a 50-ha farm, the maximum values of the internal rate of return (IRR 5 44%) and net revenue above operation costs (NR 5US$1211000) were obtained for a stocking density of 67 postlarvae (PL) m À 2 during winter^spring (cycle 1) and 65 PL m À 2 during summer^autumn (cycle 2). Regardless of the density used for cycle 1, stocking at 50 and 65 PL m^2 for cycle 2 su⁄ced to obtain, respectively, IRRs greater than the minimum attractive IRRs of 15% and 30%. A frequency distribution of IRR, projected for densities of 67 and 65 PL m À 2 , showed high con¢dence in obtaining IRR values above 15% and 30% (i.e. con-¢dence 499% and 92% respectively). The frequency distribution of NR showed that the farm could operate without economic losses. Stocking a minimum of 53% of the capacity of the farm would guarantee positive NR. Sensitivity analysis indicated that the IRR and NR were mainly in£uenced by mortality rate, selling price, density, ¢nal weight and FCR.