Reduced fish diversity despite increased fish biomass in a Gulf of California Marine Protected Area

Abstract

Multi-use marine protected areas (MUMPAs) are a commonly applied tool for marine conservation in developing countries, particularly where large no-take reserves are not socially or politically feasible. Although MUMPAs have produced benefits around the world, the persistence of moderate fishing pressure reduces the likelihood of achieving the primary objective of these areas, which is the conservation of ecosystems. In this study we used traditional and functional metrics to evaluate how fish assemblages changed through time in a MUMPA, including shifts in species responses and in ecological processes. We conducted visual censuses of fishes at Espíritu Santo Island, México (MUMPA; N = 320; 24°N, 110°W) from 2005 to 2017 to assess fish richness, size-distribution and density. Three functional indices were calculated using six traits (size, mobility, period of activity, aggregation, position in water column and diet): functional richness (volume occupied by species), dispersion (complementarity between species) and originality (inverse of functional redundancy). We compared fish diversity among three management zone types (sustainable fishing, traditional fishing and no-take zones), through a 13-year period, assessing which species increased or decreased in occurrence, density, and biomass, and how indices respond over time. Despite a general increase in biomass and stability in density and originality, we detected a reduction in fish biodiversity in the form of declines in species and functional richness, which could imply the risk of local extinction and decrease in certain ecosystem processes. In addition, changes in functional dispersion showed that some functions are losing representation through time. Although no single cause is apparent, such factors as competitive interactions, habitat loss and persistence of fishing pressure potentially explain these decreases. The rise in biomass was associated with a general increase in the average size, rather than increased biomass of commercial species, as the latter remained stable during the study period. Expansion of no-take areas, enforcement of fishing regulations, and surveillance in core zones, should be implemented to reverse the decline in particular species and to promote conservation of fish functional diversity in this MUMPA.

Environmental biomonitoring of reef fish community structure with eDNA metabarcoding in the Coral Triangle

“…In this study, we found that sites in the utility zone had the highest diversity index (H') value, in contrast to the core region where (H') ranged from low to moderate with high dominance index (D) values at each observation site for both the mid-column water and sediment samples. In general, one key measure of MPA implementation effectiveness in ecological terms is biotic community composition, and in particular fish diversity (Blowes et al 2020;Kruschel et al 2012;Ramírez-Ortiz et al 2020). The higher diversity in the utility zone compare to the core zone could be related to how the MPA is implemented.…”

Caracterización y uso de los atributos funcionales de los peces para el estudio de sus comunidades en la cuenca del río Lacantún, Chiapas

“…Descripciones detalladas de estos atributos y la definición de cada una de las categorías utilizadas pueden encontrarse en la literatura científica (Lyons et al, 1995;Mercado-Silva et al, 2002. Estos atributos, en su conjunto, pueden ser utilizados para identificar entidades funcionales (EF, especies con combinaciones únicas de atributos funcionales) (Ramírez-Ortiz et al, 2020). Además, se evaluó si las especies son nativas o exóticas en los sistemas acuáticos de la región.…”

Composición, distintividad taxonómica y diversidad beta de la ictiofauna marina del Parque Nacional Huatulco

“…Las áreas marinas protegidas son el instrumento más eficiente para manejar los recursos y mitigar las perturbaciones antropogénicas en los ecosistemas marinos, principalmente aquellas asociadas a la presión por pesca (Bates et al, 2014;Ramírez-Ortiz et al, 2020). Desde mediados de la década de los ochenta, el gobierno mexicano ha establecido varias áreas naturales protegidas (ANP) para conservar la biodiversidad y controlar la extracción de recursos (Conanp, 2007).…”