Pelagic larval growth rate impacts benthic settlement and survival of a temperate reef fish

Larvae of marine reef organisms settling into benthic habitats may vary greatly in individual quality. We evaluated potential effects of variation in larval growth rate (1 metric of quality) on larval duration, size-at-settlement, and post-settlement survival of recently settled kelp bass Paralabrax clathratus. We sampled kelp bass daily and weekly from standardized collectors located near the Wrigley Institute for Environmental Studies, Santa Catalina Island, to characterize larval traits of settlers and surviving recruits. Using growth models to fit trajectories of larval otolith growth, we estimated instantaneous larval growth rates and found that these values were good predictors of larval duration and juvenile survival. Kelp bass that grew rapidly as larvae settled ∼8.5 d sooner than the slowest growing individuals; both groups had similar sized individuals at settlement, but fast growing larvae experienced enhanced survival during the first 5 d after settlement relative to slower growing larvae. There is growing evidence suggesting that larval experience continues to exert demographic consequences on subsequent life stages. This helps to explain some of the spatial and temporal variability that characterizes recruitment in marine systems.

Pelagic larval growth rate impacts benthic settlement and survival of a temperate reef fish

Larvae of marine reef organisms settling into benthic habitats may vary greatly in individual quality. We evaluated potential effects of variation in larval growth rate (1 metric of quality) on larval duration, size-at-settlement, and post-settlement survival of recently settled kelp bass Paralabrax clathratus. We sampled kelp bass daily and weekly from standardized collectors located near the Wrigley Institute for Environmental Studies, Santa Catalina Island, to characterize larval traits of settlers and surviving recruits. Using growth models to fit trajectories of larval otolith growth, we estimated instantaneous larval growth rates and found that these values were good predictors of larval duration and juvenile survival. Kelp bass that grew rapidly as larvae settled ∼8.5 d sooner than the slowest growing individuals; both groups had similar sized individuals at settlement, but fast growing larvae experienced enhanced survival during the first 5 d after settlement relative to slower growing larvae. There is growing evidence suggesting that larval experience continues to exert demographic consequences on subsequent life stages. This helps to explain some of the spatial and temporal variability that characterizes recruitment in marine systems.

Early indicators of MPA effects are detected by stereo-video

Resource managers often outline discrete goals when implementing marine protected areas (MPAs), such as increases in organism abundance, biomass, or body size, to evaluate MPA success and thus inform future management decisions. Understanding which biological indicators are most sensitive to protection is essential for adaptive management, and while density is a commonly used metric to monitor MPAs, previous work has pointed to a lack of reliability of this metric to effectively evaluate MPAs, particularly during initial stages of protection. To determine which biological indicators of MPA success were evident 5 yr after protection began, we examined the differences in populations inside vs. outside MPAs for 3 fishes targeted by anglers—kelp bass Paralabrax clathratus, barred sand bass P. nebulifer, and California sheephead Semicossyphus pulcher—and 4 non-targeted species. We used stereo-video to determine the average body size, biomass, and density of each species in 7 MPAs in Southern California that were paired with nearby non-MPA sites. Responses of targeted species were detectable after 5 yr of protection in some MPAs. In most but not all MPAs, individuals were larger compared to outside MPAs for kelp bass and California sheephead. Biomass and density of targeted species appeared to be less sensitive to MPA effects. As expected, non-targeted species did not show evidence of MPA effects. Similar to past studies, our findings indicate that the choice of response variable and species studied may influence the perceived efficacy of MPAs, and we emphasize that increases in length may be a particularly sensitive indicator of effective protection.