Geographic coupling of juvenile and adult habitat shapes spatial population dynamics of a coral reef fish

Abstract

Abstract. 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.

Highly localized replenishment of coral reef fish populations near nursery habitats

“…Our results revealed that for several species, the subsidy of reef populations by nurseries is largely localized to within ~4 km, with only little movement and spillover to more distant reef areas, and results in different reef fish community structures close to versus isolated (> 4 km) from nurseries. Distant reefs still harboured low densities of species with high and low nursery dependence, and this could be due to local recruitment or long-distance dispersal of older individuals away from nurseries (Huijbers et al 2013). Previous studies have confirmed that in the absence of nursery habitats, background densities of nursery species on reefs are low to zero, depending on the species (Nagelkerken et al 2002, Dorenbosch et al 2005), but our study provides new insights into density changes on reefs that lie on the gradient between connected and isolated reefs.…”

“…Home range and dispersal probability usually increase with growing body size (Bradbury et al 2008). This is especially true for large lutjanids (snappers) that have excellent swimming capabilities and are able to disperse 10s of km, and sometimes up to a few hundred km from their nursery sites (Nagelkerken 2009, Huijbers et al 2013. N evertheless, movement is risky (Turgeon et al 2010) and fishes migrating from nurseries onto reefs would be expected to reduce (but not completely avoid) their dispersal to more isolated reefs as long as local resources and conditions remain favourable for survival and growth.…”

“…Furthermore, we se lected our sites in such a way that the gradient of reef sites was located close to only a single nursery area, to reduce possible influxes from other nursery patches that were not included. Although we did not tag the observed fishes to determine their origin, we have previously shown, using stable isotope signatures in otoliths and muscle tissue of the yellowtail snapper Ocyurus chrysurus (a high-dependence species) and French grunt Haemulon flavolineatum (a low-dependence species), that even though adults can disperse over long distances, most (but not all) of the dispersal from nurseries onto reefs is concentrated at their nearest nursery habitat in Curaçao and Bonaire (Verweij et al 2008, Huijbers 2012, Huijbers et al 2013, and a similar mechanism has been confirmed for several Indo-Pacific species (e.g. Nakamura et al 2008, Kimirei et al 2013b, Paillon et al 2014.…”

“…However, there have been few formal tests of the hypothesis that the influence of nurseries on coral reef population replenishment decreases with distance from nurseries (Mumby 2006, Huijbers et al 2013. There is still a lack of understanding of how far young animals disperse and up to what distances nurseries affect adult community structure.…”

Variación entre hábitats de la densidad y composición por tallas en peces de arrecife de la región noroccidental de Cuba

“…Huijbers, Nagelkerken, Debrot & Jongejans (2013) found that the contribution of the coral reef as a nursery habitat for O. chrysurus was minimal. We found relatively high abundances of juveniles of this species in all reef habitats except mangrove roots.…”