Abundance patterns for three species of penaeid shrimp off northwestern Mexico are explained based on sampling-catch data obtained by the National Fisheries Institute during closed fishing seasons (1995–2006). The bathymetry and fishing area (>14,000 km2) were determined from a depth dataset of >45,000 points. The catch data were obtained from a sampling network of 62 sites, with an average of 76 trawls per fishing season; the brown shrimp (Farfantepenaeus californiensis) was the most abundant species. The relative abundance models for the three species, produced by two geostatistical methods (inverse distance weighting (IDW) and Kriging), identified mid-northern Sinaloa as the most important area regarding the distribution of the resource, with each species displaying different distribution patterns. The spatial model allowed the categorization of data into three levels of relative abundance, taking the values between quartiles 1 and 3 as the medium abundance and the values below quartile 1 and above quartile 3 as the extremes (low and high). The two geostatistical techniques (IDW and Kriging) produced very similar abundance distribution maps, with values >0.7 of the Kappa index of agreement, particularly for areas of high abundance. These results could be useful to point out those areas that can be used to regulate fishing effort and reduce fishing mortality, supporting the sustainable development of the fishery.

There are few comprehensive studies on the condition of reefs that are remote from direct anthropogenic pressures and, therefore, ecological baseline data are scarce. To help address this deficiency, the community condition of the little-studied remote reefs along a 200-kmlong tract bordering the Gulf of Batabano (southwest Cuba) was assessed. The reef-front coral communities (38 sites), where Montastraea spp. is the most common coral, were homogeneous along the entire reef tract. The reef-crest coral communities (30 sites), however, could be differentiated into three geographically distinct areas by their abundances of Acropora palmata and Diploria clivosa; the former predominated at 26 of the 30 reef-crest sites, but most colonies were “standing dead”. This observation is similar to the massive declines of acroporid coral populations that have been documented throughout the Caribbean region. Mean coral cover (19–26%) was similar to the regional average (19–23%), but was surprisingly high (72%) at a protected reef-crest site close to an extensive mainland coastal mangrove (Ciénaga de Zapata). At this site, A. palmata and other acroporids were abundant and healthy, and Diadema antillarum density was higher than in the other surveyed areas. Reduced hurricane impact at this more sheltered site may have either circumvented a synergy with overfishing, hurricane destruction, and recruitment failure (widely reported at other degraded reefs), or maintained a high diademid population that facilitated coral recruitment and allowed rapid coral recovery following damage. Key words: AGRRA, coral reef, Diadema, health assessment, hurricanes, Cuba

Mangroves occur in coastal areas and are therefore vulnerable to anthropogenic disturbance and exhibit high rates of deforestation. Mexico is among the countries with the highest degree of mangrove deforestation in America; however, precise data on national mangrove coverage in Mexico is incomplete, making it impossible to accurately ascertain the rate of mangrove loss over time. Precise information is necessary to assess changes at local and regional scales to detect the magnitude, trends, and drivers of the transformation. This study aimed to estimate the loss of mangrove cover in the area of Mahahual-Xcalak (Quintana Roo, Mexico) between 1995 and 2007, to calculate the annual deforestation rate and to identify the drivers of deforestation. Landsat TM and ETM+ images from 1995 and 2007 were used to estimate the loss of mangrove cover using a multitemporal analysis. Semi-structured interviews with local residents of Mahahual and Xcalak were undertaken to identify and validate the drivers of deforestation. The image analysis for the 12-year period showed that 1070 ha of mangrove forest have been lost, with an annual deforestation rate of 0.85%—a relatively high value compared with other mangrove regions in Mexico. The main factor that has triggered the reduction of mangrove coverage is the expansion of anthropogenic land uses (e.g., settlements and roads). This study concludes that conservation and rehabilitation programs need to be implemented so that the Mahahual-Xcalak mangrove environment can continue to provide key ecosystem services

Total replacement of cod liver oil by vegetable oils in the diets of juvenile California halibut (Paralichthys californicus) was analyzed. Five diets were formulated with olive oil, corn oil, linseed oil, and two combinations of linseed oil and corn oil, and compared with a control diet containing cod liver oil during a 12-week feeding experiment. Highest growth was observed in fish fed the control diet; however, no significant differences in growth and survival were observed among the dietary treatments. The fatty acids from linseed, corn, and olive oils were the most accumulated in the tissue, increasing in proportion to the total fatty acids. Reduced levels of 20:5n-3 and 20:4n-6 in the presence of high dietary levels of 18:3n-3 and 18:2n-6 suggest that, as in most marine fishes, synthesis of 18:3n-3 to 20:5n-3 and of 18:2n-6 to 20:4n-6 is either very limited or does not occur. Although the content of 22:6n-3 in the muscle of fish fed the control diet was approximately 2.0 to 2.5 times greater than that in the muscle tissue of fish fed the experimental diets, no significant differences were detected. A proportional decrease in 20:5n-3 among all fatty acids and a lack of an increase in body tissue suggest that this fatty acid was being used to synthesize 22:6n-3. The significant reductions in the level of 20:5n-3 indicate that if the experiment had been conducted over a longer period of time, a level would eventually be reached whereby the dietary deficiency would presumably be reflected by an adverse effect on growth. Additional research is needed, particularly regarding the proportional and quantitative changes of 20:5n-3 and 22:6n-3 in the composition of the muscle tissue

The incidental capture of sea turtles by industrial shrimp trawlers off eastern Venezuela is documented, based on data gathered by on-board observers from February 1991 through November 2000. A total of 275 trips were made, with a total of 55,992 h of trawling using either one or two normal nets of 20-m headrope length, equivalent to 59,744 h std. net–1 of 30.5 m upper rope length. In total, 63 turtles were captured: 20 Eretmochelys imbricata, 20 Chelonia mydas, 15 Caretta caretta, and 8 Dermochelys coriacea. All these species showed a wide distribution along the central Caribbean Sea and Atlantic coasts of Venezuela, but they were always caught in areas close to shore and not deeper than 82 m; the distribution of D. coriacea was more concentrated towards the Atlantic zone. The estimated CPUE for all four species, using non-standardized effort values, was 0.0011 ± 0.0003 turtles h–1 std. net, equivalent to one turtle per 930 ± 11 h std. net. The variation in captures throughout the year was not significant (chi-square = 1.29; P = 0.73), except for D. coriacea, which was only caught between January and May. No significant difference was observed between the capture of turtles during the day or night. Direct mortality ratio reached 19 ± 9.7%; the actual ratio of mortality caused by incidental capture is not known. Most individuals caught by Venezuelan trawlers were juveniles that most probably use the area as feeding grounds. Considering an average effort by the fleet of 310,000 ± 16,500 h std. net yr–1, an estimate of turtle capture before the use of turtle excluder devices was made mandatory in 1994 would be about 330 ± 4 ind yr–1, with an associated direct mortality of 63 ± 30 turtles. This capture rate would be the lowest among the countries where similar evaluations have been performed (Australia, Colombia, Costa Rica, and USA). Key words: size structure, CPUE, distribution, Caribbean Sea.

We estimated the net flux of inorganic phosphorus (kg P d–1) due to geostrophic transport in the upper 100 m of a control volume (CV) off Baja California (Mexico) during 2003 and 2004. The influence of this flux on integrated primary production (IPP) in the photic zone (less than 100 m depth) was estimated comparing the net P flux into the CV against the P requirements for IPP. The greatest P fluxes occurred during spring and summer 2004; the northern side of the CV was the main recipient of P. The most persistent P outflow occurred along the southern side of the CV, except in winter 2003, when there was an input of P fluxes related to cyclonic and anticyclonic eddies off Ensenada. The net geostrophic transport during 2003 and 2004 contributed enough P to support the IPP requirements during winter and spring, indicating that P was not limiting for phytoplankton organic carbon production during these seasons.

Human exploitation can lead to genetic bottlenecks associated with reduced genetic variability and lower fitness. The population of California sea lions (Zalophus californianus) in the Gulf of California, Mexico, was hunted during the 19th and 20th centuries, potentially leading to a genetic bottleneck; however, even exploitation that leads to low population sizes does not always cause genetic bottlenecks. Understanding the genetic consequences of past sea lion hunts is critical to the conservation of the Gulf of California sea lion population, which is currently declining and is genetically distinct from other populations. We used available data from 10 amplified polymorphic microsatellite loci in 355 individuals from six Mexican colonies. Microsatellite data were analyzed using diverse approaches (BOTTLENECK and M-ratio) to determine if a genetic bottleneck had occurred. Our results indicate that human exploitation did not cause a genetic bottleneck in the sea lion population of the Gulf of California. Simulation analyses revealed that a reduction in genetic variability would have been detected if fewer than 100 individuals had remained after exploitation. We conclude that past exploitation was not as severe as previously thought and did not cause a genetic bottleneck in the Gulf of California sea lion population. Nevertheless, historical hunts specifically targeted adult males and this sexbiased exploitation may have influenced the population dynamics and overall fitness. Key words: genetic variability, male-biased exploitation, Pinnipedia, Gulf of California.