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Marine spatial population dynamics are often addressed with a focus on larval dispersal, without taking into account movement behavior of individuals in later life stages. Processes occurring during demersal life stages may also drive spatial population dynamics if habitat quality is perceived differently by animals belonging to different life stages. In this study, we used a dual approach to understand how stage‐structured habitat use and dispersal ability of adults shape the population of a marine fish species. Our study area and focal species provided us with the unique opportunity to study a closed island population. A spatial simulation model was used to estimate dispersal distances along a coral reef that surrounds the island, while contributions of different nursery bays were determined based on otolith stable isotope signatures of adult reef fish. The model showed that adult dispersal away from reef areas near nursery bays is limited. The results further show that different bays contributed unequally to the adult population on the coral reef, with productivity of juveniles in bay nursery habitat determining the degree of mixing among local populations on the reef and with one highly productive area contributing most to the island's reef fish population. The contribution of the coral reef as a nursery habitat was minimal, even though it had a much larger surface area. These findings indicate that the geographic distribution of nursery areas and their productivity are important drivers for the spatial distribution patterns of adults on coral reefs. We suggest that limited dispersal of adults on reefs can lead to a source–sink structure in the adult stage, where reefs close to nurseries replenish more isolated reef areas. Understanding these spatial population dynamics of the demersal phase of marine animals is of major importance for the design and placement of marine reserves, as nursery areas contribute differently to maintain adult populations.

Recent empirical studies have demonstrated that human activities such as fishing can strongly affect the natural capital and services provided by tropical seascapes. However, policies to mitigate anthropogenic impacts can also alter food web structure and interactions, regardless of whether the regulations are aimed at single or multiple species, with possible unexpected consequences for the ecosystems and their associated services. Complex community response to management interventions have been highlighted in the Caribbean, where, contrary to predictions from linear food chain models, a reduction in fishing intensity through the establishment of a marine reserve has led to greater biomass of herbivorous fish inside the reserve, despite an increased abundance of large predatory piscivores. This positive multi-trophic response, where both predators and prey benefit from protection, highlights the need to take an integrated approach that considers how numerous factors control species coexistence in both fished and unfished systems. In order to understand these complex relationships, we developed a general model to examine the trade-offs between fishing pressure and trophic control on reef fish communities, including an exploration of top-down and bottom-up effects. We then validated the general model predictions by parameterizing the model for a reef system in the Bahamas in order to tease apart the wide range of species responses to reserves in the Caribbean. Combining the development of general theory and site-specific models parameterized with field data reveals the underlying driving forces in these communities and enables us to make better predictions about possible population and community responses to different management schemes.

The fishes of the Lutjanidae family are widely distributed throughout the Atlantic, Indian and Pacific Oceans and have relevant commercial importance. Yellowtail snapper (Ocyurus chrysurus) is a targeted species in the small-scale fishery of the northeastern coast of Brazil, notably for hand-line fishing. We used the local ecological knowledge (LEK) of three generations of fishers from Ilhéus (southern Bahia State, Brazil) to evaluate the perception of weight, best day of capture and relative abundance of the species. More experienced fishers captured the largest specimens, had larger catches and were more likely to indicate a decrease in species abundance. On the other hand, younger fishers had smaller catches and were more likely to indicate that the species abundance is stable or increasing. The results suggest the occurrence of shifting baseline syndrome among fishers and emphasize the importance of including information from fishers in the construction of management measures. Fishers can play a key role in developing viable proposals that are aimed at the management of fishing of species with spawning aggregation, such as yellowtail snapper.

This article estimated delayed mortality in yellowtail snapper that would be discarded in the fishery due to size regulations. Delayed mortality was estimated through reflex impairment and blood parameters associated with the stress response.AbstractYellowtail snapper (Ocyurus chrysurus) is an important part of the reef fish assemblage in the western, tropical Atlantic and is caught by both recreational and commercial fisheries in south Florida and the Bahamas. It is estimated that 80% of snapper caught within southeastern Florida waters are discarded due to minimum size restrictions. Neglecting to include information on delayed mortality of undersized fish has the potential for fishery managers to overestimate the abundance of smaller size classes and introduce bias into stock assessments. This study examines associations between reflex impairment, traditional physiological parameters and post-release mortality of undersized yellowtail snapper. Laboratory experiments exposed yellowtail snapper to a gradient, simulating capture conditions. Blood draws were obtained from a sub-sample of fish. There was a significant relationship between delayed mortality and the proportion of reflex impairment for both individual fish and groups of fish (P < 0.001 and P = 0.03). Within the sub-sample of blood-sampled fish, base excess and pH were significantly correlated to reflex impairment. Delayed mortality was significantly correlated to pH, base excess and lactate concentration. Results suggest that discarded, undersized yellowtail with more than 29% of their reflexes impaired will not survive.