Long-term effectiveness of a multi-use marine protected area on reef fish assemblages and fisheries landings.

The Loreto Bay National Park (LBNP) is a large, multi-use marine protected area in the Gulf of California, Mexico, where several types of small-scale commercial and recreational fishing are allowed, but where less than 1% of the park is totally protected from fishing. The LBNP was created in 1996; its management plan was completed in 2000, but it was not effectively implemented and enforced until 2003. Between 1998 and 2010, we monitored reef fish populations annually at several reefs inside and outside the LBNP to measure the effects of the park on fish assemblages. We also evaluated reported fisheries landings within the LBNP for the same time series. Our results show that reef fish biomass increased significantly after protection at a small no-take site at LBNP relative to the rest of the park. However, the multi-use part of LBNP where fishing is allowed (99% of its surface) has had no measurable effect on reef fish biomass relative to open access sites outside the park boundaries. Reported fisheries landings have decreased within the park while increasing in nearby unprotected areas. Although the current partial protection management regime has not allowed for reef fish populations to recover despite 15 years as a "protected area," we conclude that LBNP's regulations and management have maintained the conditions of the ecosystem that existed when the park was established. These results suggest that community livelihoods have been sustained, but a re-evaluation of the multi-use management strategy, particularly the creation of larger no-take zones and better enforcement, is needed to improve the reef fish populations in the park in order to ensure sustainable fisheries far into the future. These recommendations can be applied to all multi-use MPAs in Mexico where ecosystem recovery is not occurring despite maintenance of fish stocks.

Including risk in stated-preference economic valuations: Experiments on choices for marine recreation.

Stated-preference surveys for the economic valuation of environmental resources typically assume no uncertainty in the hypothetical valuation scenarios. However, the outcomes of environmental policies are uncertain. We explored the effects of including information on probabilities of attribute improvement and provision in choice experiments. Our results suggest that stating explicitly a high probability for the occurrence of the valuation scenario can improve the goodness of fit of choice models and the consistency of choices. As the general public becomes more aware of the uncertainty of environmental outcomes under global change, omitting information on scenario risk may contribute to hypothetical bias and impair the validity of stated-preference valuations.

A noninvasive demographic assessment of sea lions based on stage-specific abundances.

A pressing need exists to develop new approaches for obtaining information on demographic rates without causing further threats to imperiled animal populations. In this paper, we illustrate and apply a data-fitting technique based on quadratic programming that uses stage-specific abundance data to estimate demographic rates and asymptotic population growth rates (lambda). We used data from seven breeding colonies of California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Estimates of lambda were similar to those from previous studies relying on a diffusion approximation using trends in total abundance. On average, predicted abundances were within 24% of the observed value for the inverse estimation method and within 29% of the observed value for the diffusion approximation. Our results suggest that three of the seven populations are declining (lambda < 1), but as many as six may be at risk. Elasticity and sensitivity analyses suggest that population management in most sites should focus on the protection of adults, whose survival generally contributes the most to lambda. The quadratic programming approach is a promising noninvasive technique for estimating demographic rates and assessing the viability of populations of imperiled species.

Viability analysis of reef fish populations based on limited demographic information.

Marine protected areas (MPAs) that allow some degree of artisanal fishing have been proposed to control the overexploitation of marine resources while allowing extraction by local communities. Nevertheless, the management of MPAs is often impaired by the absence of data on the status of their resources. We devised a method to estimate population growth rates with the type of data that are usually available for reef fishes. We used 7 years of spatially explicit abundance data on the leopard grouper (Mycteroperca rosacea) in an MPA in the Gulf of California, Mexico, to construct a matrix population model that incorporated the effects of El Niño/La Niña Southern Oscillation on population dynamics. An environmental model that estimated different demographic estimates for El Niño and La Niña periods performed better than a single-environment model, and a single-habitat model performed better than a model that considered different depths as different habitats. Our results suggest that the population of the leopard grouper off the main island of the MPA is not viable under present conditions. Although the impact of fishing on leopard grouper populations in the MPA has not yet been established, fishing should be closed as a precautionary measure at this island if a priority of the MPA is to ensure the sustainability of its fish populations.

A decision framework for the adaptive management of an exploited species with implications for marine reserves.

Marine reserves have both conservation and fishery benefits. Nevertheless, there are no general criteria about when and where to establish new reserves, how to evaluate their efficacy, and how to conduct adaptive management to achieve conservation goals. We applied a decision-theory framework to optimally allocate conservation resources between improving data on population status and establishing a reserve for species conservation. Our goal was to maximize reserve benefits given the constraints of a population growth rate that would permit sustainability of resources. We illustrate our decision framework with a retrospective analysis of a 7-year time series on abundance of the leopard grouper (Mycteroperca rosacea) in the Sea of Cortés, Mexico. We used the lower bound of the distribution of the population growth rate (lambda) as a decision rule for determining how many years of monitoring are needed to detect reserve effects. We determined the minimum time frame needed to estimate lambda based on a stated level of risk tolerance for four sites. As expected, the coefficient of variation for the lambda declined with the number of years of data. This increased precision with additional years of data resulted from the high degree of annual variability in the system. Where populations were slow to respond to reserves, more data were needed to detect a positive lambda value. For the leopard grouper case study, confidence in the estimate of lambda increased with the number of years of data. Our decision framework may be used to identify the minimum number of years of data needed before a management decision about reserve establishment could be made that is reasonably likely to meet its management objectives.

Coral cover and partial mortality on anthropogenically impacted coral reefs at Eilat, northern Red Sea.

A photographic analysis was conducted at five shallow reef sites (5-6 m) at Eilat (northern Red Sea) to study changes in live coral cover during a 2-year period. Logit regression analysis showed that levels of total oxidized nitrogen (TON; NO(2)+NO(3)) and the presence of SCUBA divers were significant explicative variables of coral partial mortality, while sedimentation rate was not significant. Sites exposed to mean TON levels above 0.4 microM TON showed significantly lower live stony coral cover and abundance per m(2), and higher partial mortality of coral colonies than sites exposed to lower TON. These findings may be useful in establishing limits for TON levels at Eilat, but must be interpreted with caution due to the complexity of nutrient dynamics in coral reefs, the uncertainty of the effects of nutrients on coral physiological processes, and the possibility of interactions among multiple coral stressors.