Circle Hooks In Commercial, Recreational, And Artisanal Fisheries: Research Status And Needs For Improved Conservation And Management

The intent of convening the International Symposium on Circle Hooks in Research, Management, and Conservation was to yield a contemporary, science-based assessment of the management and conservation utility of circle hooks in commercial, recreational, and artisanal fisheries around the globe. The symposium objective was to provide a forum for individuals, organizations, and agencies to share relevant research results and perspectives. Based on the presentations, an examination of the literature, and the collective experience and knowledge of the authors, we provide a brief overview of the current status of circle hook research along with a list of research needs, with a particular focus on science that has the potential to inform managers and stakeholders. Progress was made on the definition of a true circle hook. There was strong recognition that circle hooks represent just one of the tools available to managers for reducing bycatch and release mortality. Also defined was the need for an integrative approach that considers strategies that complement the use of circle hooks. Some of the research needs identified include a greater emphasis on human dimension studies to identify those factors that may impede adoption of circle hook technology by stakeholders and comparative studies of circle hook performance relative to mouth morphology, dentition, and feeding behavior. While the literature on effective use of circle hooks is growing, there remains a number of unanswered questions that will require study before circle hooks are more widely adopted for conservation and management of aquatic living resources

Dispersal of Adult Black Marlin (Istiompax indica) from a Great Barrier Reef Spawning Aggregation

The black marlin (Istiompax indica) is one of the largest bony fishes in the world with females capable of reaching a mass of over 700 kg. This highly migratory predator occurs in the tropical regions of the Pacific and Indian Oceans, and is the target of regional recreational and commercial fisheries. Through the sampling of ichthyoplankton and ovaries we provide evidence that the relatively high seasonal abundance of black marlin off the Great Barrier Reef is, in fact, a spawning aggregation. Furthermore, through the tracking of individual black marlin via satellite popup tags, we document the dispersal of adult black marlin away from the spawning aggregation, thereby identifying the catchment area for this spawning stock. Although tag shedding is an issue when studying billfish, we tentatively identify the catchment area for this stock of black marlin to extend throughout the Coral Sea, including the waters of Papua New Guinea, the Solomon Islands, Micronesia, New Caledonia, Kiribati, Vanuatu, Fiji, Tuvalu and Nauru

Distribution and Habitat Associations of Billfish and Swordfish Larvae across Mesoscale Features in the Gulf of Mexico

Ichthyoplankton surveys were conducted in surface waters of the northern Gulf of Mexico (NGoM) over a three-year period (2006–2008) to determine the relative value of this region as early life habitat of sailfish (Istiophorus platypterus), blue marlin (Makaira nigricans), white marlin (Kajikia albida), and swordfish (Xiphias gladius). Sailfish were the dominant billfish collected in summer surveys, and larvae were present at 37.5% of the stations sampled. Blue marlin and white marlin larvae were present at 25.0% and 4.6% of the stations sampled, respectively, while swordfish occurred at 17.2% of the stations. Areas of peak production were detected and maximum density estimates for sailfish (22.09 larvae 1000 m−2) were significantly higher than the three other species: blue marlin (9.62 larvae 1000 m−2), white marlin (5.44 larvae 1000 m−2), and swordfish (4.67 larvae 1000 m−2). The distribution and abundance of billfish and swordfish larvae varied spatially and temporally, and several environmental variables (sea surface temperature, salinity, sea surface height, distance to the Loop Current, current velocity, water depth, and Sargassum biomass) were deemed to be influential variables in generalized additive models (GAMs). Mesoscale features in the NGoM affected the distribution and abundance of billfish and swordfish larvae, with densities typically higher in frontal zones or areas proximal to the Loop Current. Habitat suitability of all four species was strongly linked to physicochemical attributes of the water masses they inhabited, and observed abundance was higher in slope waters with lower sea surface temperature and higher salinity. Our results highlight the value of the NGoM as early life habitat of billfishes and swordfish, and represent valuable baseline data for evaluating anthropogenic effects (i.e., Deepwater Horizon oil spill) on the Atlantic billfish and swordfish populations

Eastern Pacific reef fish responses to coral recovery following El Niño disturbances

This study examined fluctuations in an eastern Pacific reef fish assemblage as it varied with coral recovery over 30 yr. Concurrent fish and coral monitoring were conducted at Uva Island reef, which lies within the boundaries of Coiba National Park, Panama, in an area that has received virtually no fishing pressure or watershed development over the past 80 yr. Coral and fish monitoring spanned the 1982-1983 and 1997-1998 El Nino disturbances-anomalous warming events that selectively killed reef-building corals. While no fish mortalities were observed during the 1982-1983 El Nino event, live coral cover was reduced to nearly 0% at the study reef. From 1984 to 1990, live coral (Pocillopora spp.) cover was extremely low (< 5%), but demonstrated steady recovery to similar to 35% by 2010. By quantifying disturbance-related, long-term changes in coral reef resources and relating these to fish trophic group responses, several functional relationships emerged. A total of 63 fish taxa were observed, and reef fish density (all taxa combined) remained relatively stable. Multivariate analysis of species abundances revealed a strong overlap between seasons and a clustering of community composition in the years following bleaching. Fish species richness increased significantly as live coral cover rose from near 0 to 15-20% and then demonstrated a decreasing trend to 35% cover. Benthic invertivores showed a significant parabolic increase in density peaking at similar to 20% live coral cover. A pattern of decline was apparent for the mixed diet feeders guild as coral cover increased, whereas an asymptotic relationship with coral cover emerged for the facultative corallivore guild. No clear patterns in herbivore, piscivore and planktivore abundance were apparent with increasing coral cover. The varying responses of invertivore, corallivore and mixed diet feeders guilds demonstrated strong associations with coral cover, probably reflecting changes in the availability of their respective trophic resources during reef recovery. Thus, variations in coral cover probably influence fish communities through trophic pathways involving invertebrate food sources

Effects of landscape setting on oyster reef structure and function largely persist more than a decade post‐restoration

Long-term monitoring is vital to understanding the efficacy of restoration approaches and how restoration may enhance ecosystem functions. We revisited restored oyster reefs 13 years post-restoration and quantified the resident and transient fauna that utilize restored reefs in three differing landscape contexts: on mudflats isolated from vegetated habitat, along the edge of salt marsh, and in between seagrass and salt marsh habitat. Differences observed 1–2 years post-restoration in reef development and associated fauna within reefs restored on mudflats versus adjacent to seagrass/salt marsh and salt marsh-only habitats persisted more than 10 years post-restoration. Reefs constructed on open mudflat habitats had the highest densities of oysters and resident invertebrates compared to those in other landscape contexts, although all restored reefs continued to enhance local densities of invertebrate taxa (e.g. bivalves, gastropods, decapods, polychaetes, etc.). Catch rates of juvenile fishes were enhanced on restored reefs relative to controls, but to a lesser extent than directly post-restoration, potentially because the reefs have grown vertically within the intertidal and out of the preferred inundation regime of small juvenile fishes. Reef presence and landscape setting did not augment the catch rates of piscivorous fishes in passive gill nets, similar to initial findings; however, hook-and-line catch rates were greater on restored reefs than non-reef controls. We conclude that ecosystem functions and associated services provided by restored habitats can vary both spatially and temporally; therefore, a better understanding of how service delivery varies among landscape setting and over time should enhance efforts to model these processes and restoration decision-making