Seahorse populations are subject to the forces of fisheries from two fronts. They are commercially harvested for the aquarium trade, for curios, and for use in traditional Chinese medicine. They are also among the many species that are accidentally caught in large numbers in indiscriminate shrimp trawlers. In addition to decimating physical benthic habitats, shrimp trawlers are widely held responsible for declines in populations of both target and non-target species (Read et al. 2006, U.S. Commission on Ocean Policy 2004, WWF 2002, Flint and Swift 2000, Norse & Crowder 2013, Puig et al. 2012, Althaus et al. 2009). With 23 species of seahorse listed as “Data Deficient” (and 9 listed as “Vulnerable”), the scale of impact that shrimp trawlers have on populations of seahorses across the globe is unknown (IUCN 2003).
In addition to their mortality incurred as bycatch, seahorses have a long history of commercial harvest for multiple purposes. Traditional Chinese medicine has utilized dried seahorses for two millennia to treat erectile dysfunction, and recent studies have indicated that other health benefits can be gleaned from them as well, including suppression of neuroinflammatory responses and collagen release (Chang et al. 2013, Himaya et al. 2012, Ryu et al. 2010). In addition to their use in traditional Chinese medicine, seahorses that are collected dead are sold as curiosities (Vincent et al. 2011). Seahorses collected live are used for aquarium or hobbyist purposes (FAO 2010). Estimates for the number of seahorses harvested annually range widely and could be on the order of tens of millions or hundreds of millions (Save Our Seahorses, The International Seahorse Trust 2010, Vincent et al. 2011). Bruckner et al. 2005, in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) proceedings on seahorse conservation and trade, reports that seahorse landings just in Florida at the time were 120 million pounds per year, an estimated value of $200 million per year. Landings for seahorse fisheries in other parts of the world are less closely monitored. The market demand for seahorses is highest in East Asia for traditional Chinese medicine. There, some lines of evidence suggest an increase in the market demand for seahorses can be at least partially attributed to the coinciding overexploitation and collapse of sea cucumber stocks by way of shifting fishing effort (Taylor et al. 2007). This economic demand for seahorses from several different markets poses an ongoing challenge for conservation efforts.
In 1996, seahorses were listed as “Vulnerable” on the International Union for Conservation of Nature (IUCN) Red List. As the global authority on conservation and sustainable use of natural resources, the IUCN Red List is often one of the most effective approaches to conservation because the information it provides is used by “government agencies, wildlife departments, conservation-related non-governmental organizations (NGOs), natural resource planners, educational organizations, students, and the business community” to inform conservation decisions (IUCN 2016).
Out of this listing came the decision to list the entire Hippocampus genus under Annex II of CITES. This 2002 decision came into effect in 2004 and heavily restricted the international trade of seahorses, including imposing a minimum size limit on traded individuals. Restrictions are specified on the CITES website:
“International trade in specimens of Appendix-II species may be authorized by the granting of an export permit or re-export certificate. No import permit is necessary for these species under CITES (although a permit is needed in some countries that have taken stricter measures than CITES requires). Permits or certificates should only be granted if the relevant authorities are satisfied that certain conditions are met, above all that trade will not be detrimental to the survival of the species in the wild. (See Article IV of the Convention)”
During the CITES proceedings on seahorse conservation and trade, the only fisheries management strategy more highly favored among all stakeholders than minimum size limits (which were ultimately implemented by CITES) was the construction of marine protected areas (MPAs) (Bruckner et al. 2005). Though this can be legally challenging in areas beyond national jurisdiction, seahorses are most commonly found in nearshore waters, bringing the burden of responsibility of management of seahorse fisheries onto the coastal State. Many coastal States have no problem constructing MPAs for the conservation of marine biodiversity, but the ongoing delimitation disagreements in the seas off the coast of East Asia (see map 1) has resulted in a “race to fish” and a disincentive for neighboring States to cooperate to achieve conservation-oriented spatial planning objectives. Additionally, there is considerable debate surrounding the efficacy of MPAs as a conservation measure (Claudet et al. 2011, Pina-Amargós et al. 2014, Selig and Bruno 2012, Chape et al. 2005, Goni et al. 2011, Halpern 2003), and many contend that different species respond differently to different levels of protection afforded to marine protected areas. Indeed, Harasti et al. 2014 in particular indicates that seahorse predator abundance increases inside some designated MPAs and could be responsible for driving seahorse abundance down.
With a global range, seahorses are particularly abundant in the tropics and are often found in sheltered habitats: seagrass beds, estuaries, coral reefs, mangrove forests, and oyster beds (Bruckner et al. 2005). These coastal habitats are often sites of human development, especially in Florida, and these activities can be detrimental to nearby marine species. Three species of seahorse are found off the coast of Florida: Hippocampus erectus, Hippocampus reidi, and Hippocampus zosterae.
FLORIDA SEAHORSE FISHERY
Florida is the only State in the United States that issues licenses for the commercial harvest of seahorses. Florida issues about 40 of these Marine Life Transferable Dive Endorsement (MLD) and Marine Life Non-Transferable Dive Endorsement (MLN) licenses per year, in addition to Marine Life Bycatch Endorsements (MLBs) that permit license-holders to sell seahorses caught as bycatch (often in trawls). Recreational fishing for seahorses is not permitted in the State of Florida. In addition to these regulations, there are gear restrictions for the harvest of seahorses in Florida State waters and the surrounding Exclusive Economic Zone (EEZ, where the federal government maintains “jurisdiction and control” over fisheries and offshore oil and gas resources). Section 68B-42.007 of the Florida Administrative Code specifically states that the only gear types permitted for this use are: hand-held nets, barrier nets, drop nets, slurp guns, quinaldine sulphate, and trawls. In other countries, fishers collecting live seahorses for the aquarium trade will often use cyanide, which is known to have detrimental effects on other marine species as well as the physical habitat (Scales 2009). In Florida, the use of quinaldine sulphate is permitted to achieve the same facilitation of capture and transport of live fish. It is widely considered a safer and more sustainable alternative to cyanide fishing (Ross and Ross 2009). As for the permitted use of trawls to collect live seahorses, section 68B-42.007 places heavy restrictions on the size and type of trawl allowed for this use. In many other countries, seahorses are fished indiscriminately and without regard to species. But in Florida, the bag limit is 400 dwarf seahorses (Hippocampus zosterae) per person or per vessel per day, whichever is less. The efficacy of enforcement measures behind this is unclear, but the species are not difficult to distinguish and it is likely that the domestic market demand for dwarf seahorses exceeds any market for the other two species (Scales 2009).
DATA AND METHODS
Florida also has a complicated network of MPAs off its coast. For this study, several data sets were compiled: Florida commercial seahorse fishery data from the Florida Fish and Wildlife Conservation Commission (FWC) website dating back to 1990, fisheries-independent monitoring data from Ocean Biogeographic Information Systems (OBIS) spanning the period from 1882 to 2014, information on all zones where commercial seahorse fishing is effectively prohibited also from the FWC website (no-access zones, no-take zones, and zones where all commercial fishing activities are prohibited), and location information on the preferred habitats of seahorses off the coast of Florida also from the FWC website (including mangroves, seagrasses, coral, hardbottom, and oyster beds – any nearshore environment that provides holdfasts).
Though the designation of these unfished zones was not completed with the conservation of seahorses in particular in mind, the fisheries-independent monitoring data suggests that the designation of these zones has been beneficial nonetheless (see map 2). 38% of all observations were recorded within unfished areas (no-access, no-take, and no commercial fishing), 41% of observations after the implementation of listing Hippocampus under Appendix II of CITES in 2004 were recorded within unfished areas, and 41% of unfished areas are suitable habitat for seahorses (mangrove, seagrass, coral, hardbottom, oyster beds, or any combination of these). These findings demonstrate some evidence that the MPAs (here specified as unfished areas for the purposes of evaluating seahorses alone) as currently demarcated have been effective at providing and protecting suitable habitat for seahorses.
The Florida commercial fishery dependent data available for analysis is limited in scope and does not include location information or information specific to individual fishers. The units of measure are also unclear, and further investigation yielded no clarification (personal communication, April 17 2017). Available data for each year since 1990 included: number of seahorses caught, number of trips taken, estimated total value of landings, and average price per unit of seahorse. Graphing these limited aspects of the fishery nevertheless yielded some interesting results. Landings and fishing effort appeared to follow each other prior to 2004, when the CITES listing was implemented (see figure 1). After 2004, however, the gap between the effort and the resulting landings are substantial, suggesting that either the efficiency of fishers decreased or the stocks have decreased. The implementation of the CITES listing is not necessarily the driving factor of this trend, but other potential contributing factors are beyond the scope of this paper. Comparing the estimated total value of landings and the average price per unit of seahorse from year to year (see figure 2), the two track each other in an upward trend. A 1994 peak in estimated total value deviating from this general trend can be at least partially attributed to the corresponding peak in landings that occurred the same year. Finally, the roughly inverse relationship between landings and average price per unit exhibited in figure 3 reflect the fluctuations in the domestic market for seahorses resulting from the economic principle of supply and demand.
Lack of data poses a challenge for the management of the seahorse fishery in Florida. Here and in other places where lack of data is the primary roadblock to seahorse conservation efforts, research conducted and coordinated primarily by Project Seahorse will continue to facilitate the implementation of best management practices. Project Seahorse has also been instrumental in raising awareness and coordinating with political agencies and international non-governmental organizations to get seahorses listed on the IUCN Red List as well as CITES Appendix II.
But it is clear from the CITES proceedings that the only fisheries management strategy not already implemented that is highly favored among all stakeholders is the construction of marine protected areas (MPAs) (Bruckner et al. 2005). But in order to achieve effective conservation of seahorses and their habitat via marine spatial planning, coastal States must individually commit to protecting stocks in their territorial seas and EEZs from overexploitation. This is because seahorses are most commonly found in nearshore habitats, which further reinforces the importance of demarcating and managing MPAs because these habitats are the most sensitive and subject to the most and largest anthropogenic threats. Because the largest market for seahorses exists in East Asia for Traditional Chinese Medicine, it is of utmost importance for coastal States in this region to commit to zoning areas for conservation rather than exploitation. However, the much larger issue of marine delimitation conflicts in the South China Sea complicate the issue and stagnate efforts to construct MPAs for conservation.
Interested in learning more about seahorse conservation? Check out Project Seahorse!
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MAPS AND FIGURES