RESUMO
In this work a non-parametric multivariate analysis was used to assess the impact of metals and organic compounds in the macro infaunal component of the mollusks benthic community using surface sediment data from several monitoring programs collected over 20 years in Salina Cruz Bay, Mexico. The data for benthic mollusks community characteristics (richness, abundance and diversity) were linked to multivariate environmental patterns, using the Alternating Conditional Expectations method to correlate the biological measurements of the mollusk community with the physicochemical properties of water and sediments. Mollusks community variation is related to environmental characteristics as well as lead content. Surface deposit feeders are increasing their relative density, while subsurface deposit feeders are decreasing with respect to time, these last are expected to be more related with sediment and more affected then by its quality. However gastropods with predatory carnivore as well as chemosymbiotic deposit feeder bivalves have maintained their relative densities along time.
Assuntos
Ecossistema , Moluscos , Água do Mar , Animais , Biodiversidade , Monitoramento Ambiental/métodos , Sedimentos Geológicos/química , Chumbo/análise , México , Poluentes Químicos da Água/análiseRESUMO
Concentrations of total aromatic hydrocarbons and extractable organic matter in the water column and sediment were determined in samples collected in the course of the last 20 years from the Salina Cruz Harbor, México, to assess the degree of organic contamination. In sediments, organic compounds accumulate in shallow areas mostly associated with extractable organic matter and fine fractions. Calculated geocumulation index and enrichment factors suggest that contamination could be derived from anthropogenic activities attributed to harbor and ship scrapping activities, as well as transboundary source. Concentration of total aromatic hydrocarbons (as chrysene equivalents) ranged from 0.01 to 534 microg l(-1) in water, and from 0.10 to 2,160 microg g(-1) in sediments. Total aromatic concentration of 5 microg g(-1) is proposed as background concentration.
Assuntos
Sedimentos Geológicos/química , Hidrocarbonetos/análise , Poluentes Químicos da Água/análise , MéxicoRESUMO
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.
Assuntos
Sedimentos Geológicos/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , Monitoramento Ambiental , Sedimentos Geológicos/química , México , Água do MarRESUMO
Activities of fishermen in the Bay of La Paz, B. C. S. are focused to satisfy the local demand of fish and shellfish by using approximately 300 small outboard crafts equipped with gillnets. Sea lions in this Bay attack the fishes captured damaging both product and gear. We did experimental gillnet throws to determine the frequency and preferences of sea lions in fishing areas. 52 experimental gillnet throws with time averages of 2 hr were performed, rending an average of 30 kg of fish captured and less than 10% of damages to the net.. Traditional fishermen in this Bay usually left the net the whole night, (approximately 7.50 hr, obtaining an average of 50 kg of captured fish, but the damages to the nets is in average of 40%. The cost-benefit balance comparing our alternative fishing method, which includes the use of the gillnets during the afternoon, watching for sea lions and retiring the nets at their arrival, it is more sustainable and profitable than the traditional fishing method currently used by the local fishermen. This paper suggests how to minimize the harmful effects of the sea lions on the fishermen productivity and gear, maximizing the production and reducing the damage. Our alternative method is applicable to other regions where this harmful interaction is taking place. We conclude that the coexistence of sea lions-fisheries is feasible, by applying the simple measures that we propose.
Assuntos
Comportamento Animal , Pesqueiros/métodos , Peixes , Leões-Marinhos , Animais , Pesqueiros/economia , Pesqueiros/instrumentação , MéxicoRESUMO
The influence of the lunar phases on the catch-per-unit effort (CPUE) of the striped marlin (Tetrapturus audax) captured by the Cabo San Lucas, Baja California Sur, Mexico sport-fishing fleet from October 1987 to June 1989 was analyzed. The information is from 3,377 fishing trips by 13 vessels that represent about 10% of the fleet. The analysis of the CPUE showed a maximum in January 1988 and a minimum in February 1989. Taking into account the knowledge of the factors that had influence on the fishing success is important in the resource management. No significant difference during the full moon compared with results during other lunar phases was found.
Assuntos
Humanos , Animais , Pesqueiros , México , Lua , EsportesRESUMO
The influence of the lunar phases on the catch-per-unit effort (CPUE) of the striped marlin (Tetrapturus audax) captured by the Cabo San Lucas, Baja California Sur, Mexico sport-fishing fleet from October 1987 to June 1989 was analyzed. The information is from 3,377 fishing trips by 13 vessels that represent about 10% of the fleet. The analysis of the CPUE showed a maximum in January 1988 and a minimum in February 1989. Taking into account the knowledge of the factors that had influence on the fishing success is important in the resource management. No significant difference during the full moon compared with results during other lunar phases was found.
Assuntos
Peixes , Lua , Esportes , Animais , Humanos , MéxicoRESUMO
The ichthyofauna fished in BahÝa de Navidad, Jalisco, Mexico in the Central Pacific was surveyed during 1998. Six thousand nine hundred and fourty-four organisms of 130 species were caught which weighted 3,231 kg. Nearly 30 of the species belonged to Carangidae. Haemulidae and Sciaenidae. The most important species in number and biomass were Microlepidotus brevipinnins, Caranx caninus and C. caballus. Species number, abundance and biomass fluctuated during the year. The largest number of species was caught in June (61), the minimum in March (33). January had the maximum abundance (1,397 organisms), while the minimum was obtained during August (251). The maximum biomass values were from January (556.5 kg), and the lowest from August (114.7 kg). Eighteen species accumulated 87 of the total abundance, while 20 species represented 86.3 of the biomass. There were large in differences species number, abundance and biomass nets of different mesh size.
Assuntos
Animais , Elasmobrânquios , Água do Mar , Tempo (Meteorologia) , Biomassa , Clima , Pesqueiros , México , Oceano Pacífico , Densidade Demográfica , Estações do Ano , VentoRESUMO
The ichthyofauna fished in Bahía de Navidad, Jalisco, Mexico in the Central Pacific was surveyed during 1998. Six thousand nine hundred and fourty-four organisms of 130 species were caught which weighted 3,231 kg. Nearly 30% of the species belonged to Carangidae. Haemulidae and Sciaenidae. The most important species in number and biomass were Microlepidotus brevipinnins, Caranx caninus and C. caballus. Species number, abundance and biomass fluctuated during the year. The largest number of species was caught in June (61), the minimum in March (33). January had the maximum abundance (1,397 organisms), while the minimum was obtained during August (251). The maximum biomass values were from January (556.5 kg), and the lowest from August (114.7 kg). Eighteen species accumulated 87% of the total abundance, while 20 species represented 86.3% of the biomass. There were large in differences species number, abundance and biomass nets of different mesh size.
Assuntos
Elasmobrânquios/classificação , Água do Mar , Tempo (Meteorologia) , Animais , Biomassa , Clima , Pesqueiros , México , Oceano Pacífico , Densidade Demográfica , Estações do Ano , VentoRESUMO
We studied how waterbirds used two small estuaries during the non-breeding season of 1995-1996. These estuaries, El Chorro and Majahuas, were located in the middle of a large span of non-wetland habitat along the Pacific coast of México. Whereas El Chorro was basically a large and open waterbody, Majahuas was a long and narrow corridor flanked by mangroves. The two estuaries had 77 species throughout our study, but shared only 58, due to differences in their habitat. Seabirds comprised 66% of all the birds; grebes, ducks and rails 16%; shorebirds 12% and herons and egrets 5%. During late winter and early spring a very reduced number of migratory species accounted for the dominance of seabirds. Sterna hirundo and Phalacrocorax brasilianus accounted for 40 and 33%, respectively, of all the seabirds. Opening or closure of the estuary mouth at El Chorro affected the bird communities at both sites, by exposing or inundating a large mudflat in that estuary. Overall, however, time of the year was more important in the composition of the bird assemblages. Both estuaries should be considered as a single unit.
Assuntos
Aves/classificação , Animais , México , Reprodução , Estações do Ano , Água do Mar , ÁguaRESUMO
Diurnal raptors were counted monthly in the "Playón de Mismaloya", reserve, Jalisco, Mexico, from November 1997 to October 1998. We identified 11 species; eight of them migrants, one resident and two resident with migrant populations. The highest increase in total number of individuals was from December to March, influenced mainly by the presence of Caracara polancus (Crested Caracara), Falco sparverius (American Kestrel) and Pandion haliaetus (Osprey). The two former species were observed frequently in open areas, where they could detect prey more easily, while ospreys were found only in estuaries, lagoons and beach, where food was available.