Gustavo Paredes

Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes.

A global survey of reef fishes shows that the consequences of biodiversity loss are greater than previously anticipated as ecosystem functioning remained unsaturated with the addition of new species. Additionally, reefs worldwide, particularly those most diverse, are highly vulnerable to human impacts that are widespread and likely to worsen due to ongoing coastal overpopulation.

Fishing Down Coastal Food Webs in the Gulf of California

Abstract We used information from interviews with fishers, fisheries statistics, and field surveys to document changes in fisheries and fish assemblages in shallow coastal habitats in the Gulf of California, Mexico. Coastal food webs in the Gulf of California have been “fished down” during the last 30 years–fisheries shifted from large, long-lived species belonging to high trophic levels to small short-lived species from lower trophic levels. In addition, the maximum individual length of the landings has decreased about 45 cm in only 20 years. Although some catches are stagnant or still increasing for some species groups, catch-per-unit-effort declined for most species groups after 1980. These declines were associated to a dramatic increase in fishing effort in the region in the late 1970s-early 1980s, mostly in the number of gillnets. Fishing not only impacted target species, but also caused community-wide changes. These results suggest that coastal fisheries in the Gulf of California are unsustainable a...

PREDICTABILITY OF REEF FISH RECRUITMENT IN A HIGHLY VARIABLE NURSERY HABITAT

There has been a lengthy debate on whether the abundance of adult reef fishes depends on prerecruitment or postrecruitment processes; however, we still do not have the ability to predict the magnitude of local fish recruitment. Here we show that the success of the leopard grouper (Mycteroperca rosacea) recruitment in the Gulf of California, Mexico, is determined by the availability of nursery habitat, which in turn is strongly correlated to climate conditions. Observational and experimental studies showed that leopard grouper larvae recruit preferentially on shallow rocky bottoms with brown algal (Sargassum spp.) beds, and that abundance of recruits is determined by the availability of Sargassum. The biomass of Sargassum decreases linearly with an increase in the Multivariate El Niño Southern Oscillation (ENSO) Index (MEI; an index positively correlated with water temperature and negatively correlated with nutrient availability). We analyzed the relationship between the interannual variation of MEI and the recruitment of the leopard grouper using field estimates of abundance of juvenile groupers. Our results show that there is a nonlinear relationship between recruitment and the oceanographic climate, in that the density of recruits decreases exponentially with increasing MEI. The predictability of leopard grouper recruitment has important implications for fisheries management, since it could allow adaptive management without expensive stock assessment programs.