Continental-scale variation in otolith geochemistry of juvenile American shad (Alosa sapidissima)

Author Posting. © NRC Research Press, 2008. This article is posted here by permission of NRC Research Press for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 65 (2008): 2623-2635, doi:10.1139/F08-164.We assembled a comprehensive atlas of geochemical signatures in juvenile American shad (Alosa sapidissima) to discriminate natal river origins on a large spatial scale and at a high spatial resolution. Otoliths and (or) water samples were collected from 20 major spawning rivers from Florida to Quebec and were analyzed for elemental (Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca) and isotope (87Sr:86Sr and δ18O) ratios. We examined correlations between water chemistry and otolith composition for five rivers where both were sampled. While Sr:Ca, Ba:Ca, 87Sr:86Sr, and δ18O values in otoliths reflected those ratios in ambient waters, Mg:Ca and Mn:Ca ratios in otoliths varied independently of water chemistry. Geochemical signatures were highly distinct among rivers, with an average classification accuracy of 93% using only those variables where otolith values were accurately predicted from water chemistry data. The study represents the largest assembled database of otolith signatures from the entire native range of a species, encompassing approximately 2700 km of coastline and 19 degrees of latitude and including all major extant spawning populations. This database will allow reliable estimates of natal origins of migrating ocean-phase American shad from the 2004 annual cohort in the future.This work was funded by National Science Foundation (NSF) grants OCE-0215905 and OCE-0134998 to SRT and by an American Museum of Natural History Lerner–Gray Grant for Marine Research and a scholarship from SEASPACE, Inc., to BDW

Larval fish dispersal in a coral-reef seascape

Free to read at publisher's site. Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km(2)) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13-19 km, with 90% of settlement occurring within 31-43 km. Mean dispersal distances were considerably greater (43-64 km) for butterfly-fish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks

Rank change and growth within social hierarchies of the orange clownfish, Amphiprion percula

Social hierarchies within groups define the distribution of resources and provide benefits that support the collective group or favor dominant members. The progression of individuals through social hierarchies is a valuable characteristic for quantifying population dynamics. On coral reefs, some clownfish maintain size-based hierarchical communities where individuals queue through social ranks. The cost of waiting in a lower-ranked position is outweighed by the reduced risk of eviction and mortality. The orange clownfish, Amphiprion percula, maintains stable social groups with subordinate individuals queuing to be part of the dominant breeding pair. Strong association with their host anemone, complex social interactions, and relatively low predation rates make them ideal model organisms to assess changes in group dynamics through time in their natural environment. Here, we investigate the rank changes and isometric growth rates of A. percula from 247 naturally occurring social groups in Kimbe Island, Papua New Guinea (5° 12′ 13.54″ S, 150° 22′ 32.69″ E). We used DNA profiling to assign and track individuals over eight years between 2011 and 2019. Over half of the individuals survived alongside two or three members of their original social group, with twelve breeding pairs persisting over the study period. Half of the surviving individuals increased in rank and experienced double the growth rate of those that maintained their rank. Examining rank change in a wild fish population provides new insights into the complex social hierarchies of reef fishes and their role in social evolution

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Genetic parental analysis reveals both local retention and large scale connectivity of clownfish in Kimbe bay

Many marine species produce larvae that can be pelagic for weeks or months and the potential for long distance dispersal by prevailing currents is extremely high. Marine populations have, in turn, been assumed to be demographically “open”, consisting of many sub-populations that are connected by larval dispersal. However recent work has consistently demonstrated high levels of self-recruitment in reef fish populations. Because of the technical difficulty of tracking larvae, direct measures of dispersal have not previously been obtained. We report on the potential of genetic parental analysis to estimate local self-recruitment and connectivity among distant areas by identifying the parent (and their location) of a new recruit settling at a certain location. We sampled (fin-clip) the entire adult population of clown fish (Amphiprion percula) from the reef around a small island, Kimbe Island, Papua New Guinea, together with new recruits from Kimbe Island and several other locations throughout Kimbe Bay. Parental analysis demonstrated significant self-recruitment (about 50%) to the Kimbe Island sub-population, but also significant connectivity among three distant locations within Kimbe Bay. As many as 10% of new recruits at these distant locations - up to 50km from Kimbe Island - were spawned by Kimbe Island adults. At small spatial scale, we observe strong retention (up to 50%) within small lagoon around Kimbe island that question about the ability of the species to achieve the pelagic larval phase within these lagoon. Finally, we demonstrate that some parents at specific sites within Kimbe Island were more efficient in producing self-recruitmenting juveniles than adults at other sites. Genetic parental analysis opens the possibility for new perspectives in understanding success of the larval phase and investigating process determining connectivity in the perspective of better management of marine population

Genetic parental analysis reveals both local retention and large scale connectivity of clownfish in Kimbe bay

Many marine species produce larvae that can be pelagic for weeks or months and the potential for long distance dispersal by prevailing currents is extremely high. Marine populations have, in turn, been assumed to be demographically “open”, consisting of many sub-populations that are connected by larval dispersal. However recent work has consistently demonstrated high levels of self-recruitment in reef fish populations. Because of the technical difficulty of tracking larvae, direct measures of dispersal have not previously been obtained. We report on the potential of genetic parental analysis to estimate local self-recruitment and connectivity among distant areas by identifying the parent (and their location) of a new recruit settling at a certain location. We sampled (fin-clip) the entire adult population of clown fish (Amphiprion percula) from the reef around a small island, Kimbe Island, Papua New Guinea, together with new recruits from Kimbe Island and several other locations throughout Kimbe Bay. Parental analysis demonstrated significant self-recruitment (about 50%) to the Kimbe Island sub-population, but also significant connectivity among three distant locations within Kimbe Bay. As many as 10% of new recruits at these distant locations - up to 50km from Kimbe Island - were spawned by Kimbe Island adults. At small spatial scale, we observe strong retention (up to 50%) within small lagoon around Kimbe island that question about the ability of the species to achieve the pelagic larval phase within these lagoon. Finally, we demonstrate that some parents at specific sites within Kimbe Island were more efficient in producing self-recruitmenting juveniles than adults at other sites. Genetic parental analysis opens the possibility for new perspectives in understanding success of the larval phase and investigating process determining connectivity in the perspective of better management of marine population

Connectivity of coral reef fish populations : estimates from transgenerational mass-marking of embryonic otoliths using enriched stable isotopes

Theoretical studies suggest that connectivity plays a fundamental role in the dynamics, community structure, genetic diversity, and resiliency to human exploitation of coral reef fishes. Modeling efforts have been hindered, however, by the paucity of empirical estimates of, and processes controlling, population connectivity in coral reef ecosystems. While progress has been made with older life stages, connectivity as a function of larval dispersal remains unresolved for most marine populations. We have developed a new technique, based on transgenerational marking of embryonic otoliths with enriched barium isotopes, to quantify population connectivity in coral reef fishes. Gravid females are injected with an enriched stable Ba isotope solution that generates a unique isotope signature in the otoliths of all larvae subsequently spawned by the individual for up to 3 months after the injection. Otoliths of juvenile fish are then scanned for the tag using laser ablation inductively coupled plasma mass spectrometry. Validated in benthic and pelagic spawning fishes, the first field study using transgenerational marking has recently being completed in Kimbe Bay, on the northern coast of New Britain, Papua New Guinea. Results suggest that natal homing of larvae may be a common life history strategy in reef fishes, and thus appropriate spatial scales for management and conservation of coral reefs are likely much smaller than previously realize

Connectivity of coral reef fish populations : estimates from transgenerational mass-marking of embryonic otoliths using enriched stable isotopes

Theoretical studies suggest that connectivity plays a fundamental role in the dynamics, community structure, genetic diversity, and resiliency to human exploitation of coral reef fishes. Modeling efforts have been hindered, however, by the paucity of empirical estimates of, and processes controlling, population connectivity in coral reef ecosystems. While progress has been made with older life stages, connectivity as a function of larval dispersal remains unresolved for most marine populations. We have developed a new technique, based on transgenerational marking of embryonic otoliths with enriched barium isotopes, to quantify population connectivity in coral reef fishes. Gravid females are injected with an enriched stable Ba isotope solution that generates a unique isotope signature in the otoliths of all larvae subsequently spawned by the individual for up to 3 months after the injection. Otoliths of juvenile fish are then scanned for the tag using laser ablation inductively coupled plasma mass spectrometry. Validated in benthic and pelagic spawning fishes, the first field study using transgenerational marking has recently being completed in Kimbe Bay, on the northern coast of New Britain, Papua New Guinea. Results suggest that natal homing of larvae may be a common life history strategy in reef fishes, and thus appropriate spatial scales for management and conservation of coral reefs are likely much smaller than previously realize