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Species-specific monitoring through large shark fin market surveys has been a valuable data source to estimate global catches and international shark fin trade dynamics. Hong Kong and Guangzhou, mainland China, are the largest shark fin markets and consumption centers in the world. We used molecular identification protocols on randomly collected processed fin trimmings (n = 2000) and non-parametric species estimators to investigate the species composition of the Guangzhou retail market and compare the species diversity between the Guangzhou and Hong Kong shark fin retail markets. Species diversity was similar between both trade hubs with a small subset of species dominating the composition. The blue shark (Prionace glauca) was the most common species overall followed by the CITES-listed silky shark (Carcharhinus falciformis), scalloped hammerhead shark (Sphyrna lewini), smooth hammerhead shark (S. zygaena) and shortfin mako shark (Isurus oxyrinchus). Our results support previous indications of high connectivity between the shark fin markets of Hong Kong and mainland China and suggest that systematic studies of other fin trade hubs within Mainland China and stronger law-enforcement protocols and capacity building are needed. [ABSTRACT FROM AUTHOR]

Since the onset of fisheries science, monitoring programs have been implemented to support stock assessments and fisheries management. Here, we take inventory of the monitoring programs of the U.S. Gulf of Mexico (GOM) surveying fish and invertebrates and conduct a gap analysis of these programs. We also compile a large monitoring database encompassing much of the monitoring data collected in the U.S. GOM using random sampling schemes and employ this database to fit statistical models to then map the spatial distributions of 61 fish and invertebrate functional groups, species and life stages of the U.S. GOM. Finally, we provide recommendations for improving current monitoring programs and designing new programs, and guidance for more comprehensive use and sharing of monitoring data, with the ultimate goal of enhancing the inputs provided to stock assessments and ecosystem-based fisheries management (EBFM) projects in the U.S. GOM. Our inventory revealed that 73 fisheries-independent and fisheries-dependent programs have been conducted in the U.S. GOM, most of which (85%) are still active. One distinctive feature of monitoring programs of the U.S. GOM is that they include many fisheries-independent surveys conducted almost year-round, contrasting with most other marine regions. A major sampling recommendation is the development of a coordinated strategy for collecting diet information by existing U.S. GOM monitoring programs for advancing EBFM. [ABSTRACT FROM AUTHOR]

Many ecosystem-based fisheries management (EBFM) measures and restoration projects have been implemented to address the stressors that have negatively affected the United States (U.S.) Gulf of Mexico (GOM). Ecosystem simulation models are useful tools for tackling EBFM and restoration questions. Here, we review the current status of ecosystem modeling efforts for the U.S. GOM and whole GOM large marine ecosystem and identify future needs to address EBFM and restoration in these regions. Existing ecosystem models of the GOM are diverse, ranging from simple conceptual and qualitative models to biogeochemical-based end-to-end models and coupled and hybrid model platforms. Many models have focused on understanding the structure and functioning of GOM ecosystems and the impacts of EBFM measures such as bycatch reduction strategies and marine protected areas. By contrast, a small number of ecosystem models have been used specifically to address the other EBFM issues of the GOM and to assess restoration efforts (e.g., marsh restoration). The demands for EBFM and state and gulf-wide restoration activities will both be increasing in the GOM. Therefore, there is a critical need to better employ and enhance existing ecosystem models of the GOM, and to develop new ecosystem models, to more comprehensively address the different EBFM and restoration needs in the region. We provide suggestions to facilitate this endeavor. The development of consistent libraries of ecosystem models and gap analyses such as ours will help fisheries scientists to effectively tackle specific resource management questions in the different marine regions of the world. [ABSTRACT FROM AUTHOR]

The Gulf of California system presents major challenges to the still developing frameworks for ecosystem-based management (EBM). It is very much an open system and is intermittently subject to important influxes of migratory visitors, including large pelagic predatory fishes and small pelagic forage fishes. These migrants include the more tropical species from the coastal ecosystems to the south and perhaps subtropical sardines and anchovies from the California Current upwelling system. In addition to the multi-annual ENSO-scale and what may seem to be rather erratic episodes of major population incursions, the Gulf presents nonstationary, transient aspects on a variety of longer time scales. Moreover, the removal of top predators by commercial and sport fisheries has introduced trends that must be affecting the entire ecosystem, and certainly the forage fishes that are their major prey base. In addition to size limits, fishing seasons, area closures and license limitations, the fishery is managed by an ad hoc adaptive management system, in which the fishing season can be shortened or additional areas closed to fishing if pre-season exploratory fishing surveys indicate a shortage of small pelagic fishes on the fishing grounds. Whether this system is likely to be sustainable in the long term is difficult to determine, given the potential for rapid changes in the system because of environmental changes and/or feedbacks within the food web. Thus it appears that innovative management frameworks, among other things utilizing the comparative method, may be required in order to determine defensible tradeoffs between precaution and resource utilization. [ABSTRACT FROM AUTHOR]

Bulk stable isotope analysis was used to assess the trophic level and foraging habitats of Caribbean reef sharks (Carcharhinus perezi) compared to three large sympatric predatory teleosts (the Nassau grouper Epinephelus striatus, black grouper Mycteroperca bonaci, and great barracuda Sphyraena barracuda) in an isolated Caribbean coral reef ecosystem. Models and empirical studies have suggested that the depletion of large-bodied sharks in coral reef ecosystems triggers a trophic cascade that could affect the benthic community, favoring algae over coral. The hypothesized cascade is based on the premise that sharks prey on large piscivorous teleost fish that in turn prey on key herbivorous fish. Analysis of nitrogen-stable isotopes (δ15N) from white muscle tissue revealed neither adult or juvenile Caribbean reef sharks were significantly enriched in 15N compared with sympatric predatory teleost species. Linear regression found no evidence of an ontogenetic increase in nitrogen with increasing body size for Caribbean reef sharks; however, there was a significant positive relationship between body size and carbon isotope (δ13C) values. These results suggest that Caribbean reef sharks in isolated systems do not act as the apex predator in coral reef ecosystems primarily feeding on large-bodied sympatric teleosts. Instead, Caribbean reef sharks form part of an upper trophic-level predator guild alongside large-bodied teleosts, which makes the predicted trophic cascade as a result of the removal of reef sharks unlikely. Moreover, the body size-δ13C relationship suggests Caribbean reef sharks exhibit ontogenetic and individual variation in where they feed. The ecological role of this species is, therefore, complex and contextual, similar to carcharhinid species in the Indo-Pacific, emphasizing the need to further elucidate the interactions between reef sharks and the overall coral reef ecosystem so as to best inform effective conservation and management of the species. [ABSTRACT FROM AUTHOR]