Evaluating the influence of marine protected areas on surf zone fish.

Marine protected areas (MPAs) globally serve conservation and fisheries management goals, generating positive effects in some marine ecosystems. Surf zones and sandy beaches, critical ecotones bridging land and sea, play a pivotal role in the life cycles of numerous fish species and serve as prime areas for subsistence and recreational fishing. Despite their significance, these areas remain understudied when evaluating the effects of MPAs. We compared surf zone fish assemblages inside and outside MPAs across 3 bioregions in California (USA). Using seines and baited remote underwater videos (BRUVs), we found differences in surf zone fish inside and outside MPAs in one region. Inside south region MPAs, we observed higher abundance (Tukey's honest significant difference [HSD] = 0.83, p = 0.0001) and richness (HSD = 0.22, p = 0.0001) in BRUVs and greater biomass (HSD = 0.32, p = 0.0002) in seine surveys compared with reference sites. Selected live-bearing, fished taxa were positively affected by MPAs. Elasmobranchs displayed greater abundance in BRUV surveys and higher biomass in seine surveys inside south region MPAs (HSD = 0.35, p = 0.0003 and HSD = 0.23, p = 0.008, respectively). Although we observed no overall MPA signal for Embiotocidae, abundances of juvenile and large adult barred surfperch (Amphistichus argenteus), the most abundant fished species, were higher inside MPAs (K-S test D = 0.19, p < 0.0001). Influence of habitat characteristics on MPA performance indicated surf zone width was positively associated with fish abundance and biomass but negatively associated with richness. The south region had the largest positive effect size on all MPA performance metrics. Our findings underscored the variability in species richness and composition across regions and survey methods that significantly affected differences observed inside and outside MPAs. A comprehensive assessment of MPA performance should consider specific taxa, their distribution, and the effects of habitat factors and geography.

Evaluación de la influencia de las áreas marinas protegidas sobre los peces de la zona de rompientes Resumen Las áreas marinas protegidas (AMP) cumplen los objetivos de conservación y manejo de pesquerías a nivel mundial, lo que genera efectos positivos en algunos ecosistemas marinos. Las zonas de rompientes y las playas arenosas, ecotonos importantes que conectan la tierra con el mar, tienen un papel esencial en el ciclo de vida de varios peces y fungen como áreas óptimas para la pesca recreativa y de sustento. A pesar de su importancia, estas áreas están poco estudiadas con respecto a la evaluación del efecto de las AMP. Comparamos la composición de peces del área de rompientes dentro y fuera de las AMP de tres bioregiones de California, EUA. Usamos chinchorros y videos submarinos con carnada (BRUVs) y descubrimos diferencias en los peces de la zona de rompientes dentro y fuera de las AMP en una región. Dentro de las AMP de la región sur observamos una mayor abundancia (diferencia significativa honesta de Tukey [DSH]  =  0.83, p = 0.0001) y riqueza (DSH  =  0.22, p = 0.0001) en los BRUV y una mayor biomasa (DSH  =  0.32, p = 0.0002) en los censos con chinchorro en comparación con los sitios de referencia. Los taxones seleccionados de peces de sustento fueron afectados de manera positiva por las AMP. Los elasmobranquios mostraron una mayor abundancia en los BRUV y una mayor biomasa en los censos con chinchorro dentro de las AMP de la región sur (DSH  =  0.35, p = 0.0003 y DSH  =  0.23, p = 0.008, respectivamente). Aunque no observamos una señal generalizada de las AMP para la familia Embiotocidae, la abundancia de Amphistichus argenteus juveniles y adultos, la especie pescada más abundante, fue mayor dentro de las AMP (prueba K­S D  =  0.19, p < 0.0001). La influencia de las características del hábitat sobre el desempeño de las AMP indicó que el ancho de la zona de rompientes está asociado de forma positiva con la abundancia y biomasa de los peces, pero de forma negativa con la riqueza. La región sur tuvo el mayor tamaño de efecto positivo sobre todas las medidas de desempeño de las AMP. Nuestros hallazgos destacan la variabilidad en la riqueza y composición de especies en todas las regiones y los censos que afectan significativamente las diferencias observadas dentro y fuera de las AMP. Una evaluación completa del desempeño de las AMP debe considerar taxones específicos, su distribución y el efecto de los factores de hábitat y la geografía.

A host-race of the cuckoo Cuculus canorus with nestlings attuned to the parental alarm calls of the host species.

The common cuckoo has several host-specific races, each with a distinctive egg that tends to match its host's eggs. Here, we show that the host-race specializing on reed warblers also has a host-specific nestling adaptation. In playback experiments, the nestling cuckoos responded specifically to the reed warbler's distinctive 'churr' alarm (given when a predator is near the nest), by reducing begging calls (likely to betray their location) and by displaying their orange-red gape (a preparation for defence). When reed warbler-cuckoos were cross-fostered and raised by two other regular cuckoo hosts (robins or dunnocks), they did not respond to the different alarms of these new foster-parents. Instead, they retained a specific response to reed warbler alarms but, remarkably, increased both calling and gaping. This suggests innate pre-tuning to reed warbler alarms, but with exposure necessary for development of the normal silent gaping response. By contrast, cuckoo chicks of another host-race specializing on redstarts showed no response to either redstart or reed warbler alarms. If host-races are restricted to female cuckoo lineages, then chick-tuning in reed warbler-cuckoos must be under maternal control. Alternatively, some host-races might be cryptic species, not revealed by the neutral genetic markers studied so far.

Learning fine-tunes a specific response of nestlings to the parental alarm calls of their own species.

Parent birds often give alarm calls when a predator approaches their nest. However, it is not clear whether these alarms function to warn nestlings, nor is it known whether nestling responses are species-specific. The parental alarms of reed warblers, Acrocephalus scirpaceus ("churr"), dunnocks, Prunella modularis ("tseep"), and robins, Erithacus rubecula ("seee") are very different. Playback experiments revealed that nestlings of all three species ceased begging only in response to conspecific alarm calls. These differences between species in response are not simply a product of differences in raising environment, because when newly hatched dunnocks and robins were cross-fostered to nests of the other two species, they did not develop a response to their foster species' alarms. Instead, they still responded specifically to their own species' alarms. However, their response was less strong than that of nestlings raised normally by their own species. We suggest that, as in song development, a neural template enables nestlings to recognize features of their own species' signals from a background of irrelevant sounds, but learning then fine-tunes the response to reduce recognition errors.