Estimating dispersal and population connectivity fortemperate reef fishes at multiple spatial scales

摘要: Knowledge of scales dispersal and levels population connectivity is critical for understanding dynamics effective management reef fishes. These processes are important for design Marine Protected Areas (MPAs) particularly if they to generate ‘spillover’ ‘recruitment effects’. Despite this, empirical data across appropriate spatial temporal limited. This the first study focus on dispersal temperate fishes in central NSW, Australia, at scales relevant implementation MPAs (100's m - 100's km). The provides: (1) data on localised benefits small relative mobility of exploited fishes; (2) baseline utility different methods (microsatellite markers otolith chemistry) determining connectivity, and potential unprotected areas. Work microsatellite markers compared genetic structure species which span post-settlement dispersal potentials this region, provides a benchmark understanding general mechanisms govern gene flow, NSW. The response exploited establishment (≤ 0.2 km2), was investigated knowledge movement. Two established MPAs were surveyed: Cabbage Tree Bay (CTB) 2.5 year old ‘no-take’ MPA, Gordon's Bay (GB) 12.5 MPA closed spear fishing only. Abundances sizes four ‘sedentary’ three ‘mobile’ within each were compared with control locations at six times over two years. Temporal variation abundances suggested that MPAs did not encompass movement most species, exception two ‘sedentary’ (Cheilodactylus fuscus Achoerodus viridis). However, generalizations could be made between estimated mobility, duration protection and MPA response. Densities legal-sized C. 2.8-times higher fish larger within GB controls. Legal more abundant shallow areas GB indicating that influences local depth distributions. Surprisingly, mean densities Acanthopagrus australis 2.6-times CTB relative controls, similar trend GB, Girella tricuspidata CTB. Response was indicative pre-existing differences between immigration rather than recruitment fish, and/or intraspecific lack detectable effect all other and differential attributed scale of MPAs, inadequate habitats or depths, recovery time, partial protection versus 'no-take' status MPAs. Overall results emphasise can have significant ecological value, even highly mobile species. Importantly, as MPAs become smaller their location habitat depth, aggregations, recruitment 'hotspots', adjacent habitats, existing pressure determining responses rates recovery. Microsatellite markers developed provide information ≤ 400 km low (Parma microlepis) high post-settlement dispersal capabilities (G. tricuspidata). It hypothesized P. microlepis would exhibit spatial pattern isolation-by-distance (IBD) these scales, whereas G. not. Genetic differentiation seven microsatellite loci microlepis, loci examined across multiple spatial scales. collected from; sites (separated by 1-2 km), nested within locations 10-50 regions 70-80 km). G. from subset locations sampled microlepis. This included five 50-60 km) spanning sampling regions (separated 70-100 There no evidence capabilities influenced structure. Broad-scale homogeneity IBD well supported both proportion total attributable to differences among regions, effectively zero (e.g. ΦPT ≤ 0.003 RST 0.004). geographic distribution diversity high polymorphism (P. HE 0.21-0.95; tricuspidata, 0.65-0.97) indicative of mutation rates, large sizes, flow. Genetic homogeneity invertebrates NSW suggests flow important to driven factors influencing pre-settlement such East Australian Current (EAC) continuity. Thus, likely in other region have durations (≥ 2 weeks). Scales may reflect demographically dispersal distances. However, it does imply populations are well connected an evolutionary perspective sizes. This reduces risks associated natural anthropogenic declines local populations. Furthermore, be conserved 99-100% species was represented reef. Future studies using genetics determine population should very low dispersal capabilities, short life spans, whose rare or patchily distributed along-shore. The use chemistry tag requires presence differences the aquatic environment translate into chemistry. Consequently, most studies environmental gradients territorial damselfish fine exclusively marine environment. Solution-based inductively coupled plasma-mass spectrometry used measure the integrated individual reflective average environmental differences by 10-50 Mean concentrations of Sr/Ca, Ba/Ca, Mg/Ca, Mn/Ca, Cu/Ca, Zn/Ca multi-element signatures varied among sites. Fine accounted majority the variability there unique chemistries some and locations. Multi-element good discriminators, 75-80% fish correctly classified collected. difficult establish simple causal relationships elements. regional multielement signatures correlated behaviour EAC delivers water masses varying chemistry, temperature salinity regions. Results demonstrate magnitude variability open coastal regions such facilitates population connectivity < km. The thesis clear implications NSW, testable hypotheses, priorities future research. demonstrate the ecological value protecting well as population representative broader-spatial scales. determination of scales 'spillover' eggs, larvae adults remains greatest challenge. study suggests will limit providing information NSW. Given a combination artificial tags, modelling promising techniques studies. Such demonstrated localised responses fuscus, A. australis).