Julia K. Baum

Rebuilding Global Fisheries

Fighting for Fisheries In the debate concerning the future of the worlds fisheries, some have forecasted complete collapse but others have challenged this view. The protagonists in this debate have now joined forces to present a thorough quantitative review of current trends in world fisheries. Worm et al. (p. 578) evaluate the evidence for a global rebuilding of marine capture fisheries and their supporting ecosystems. Contrasting regions that have been managed for rebuilding with those that have not, reveals trajectories of decline and recovery from individual stocks to species, communities, and large marine ecosystems. The management solutions that have been most successful for rebuilding fisheries and ecosystems, include both large- and small-scale fisheries around the world. Catch restrictions, gear modification, and closed areas are helping to rebuild overexploited marine ecosystems. After a long history of overexploitation, increasing efforts to restore marine ecosystems and rebuild fisheries are under way. Here, we analyze current trends from a fisheries and conservation perspective. In 5 of 10 well-studied ecosystems, the average exploitation rate has recently declined and is now at or below the rate predicted to achieve maximum sustainable yield for seven systems. Yet 63% of assessed fish stocks worldwide still require rebuilding, and even lower exploitation rates are needed to reverse the collapse of vulnerable species. Combined fisheries and conservation objectives can be achieved by merging diverse management actions, including catch restrictions, gear modification, and closed areas, depending on local context. Impacts of international fleets and the lack of alternatives to fishing complicate prospects for rebuilding fisheries in many poorer regions, highlighting the need for a global perspective on rebuilding marine resources.

Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean

Impacts of chronic overfishing are evident in population depletions worldwide, yet indirect ecosystem effects induced by predator removal from oceanic food webs remain unpredictable. As abundances of all 11 great sharks that consume other elasmobranchs (rays, skates, and small sharks) fell over the past 35 years, 12 of 14 of these prey species increased in coastal northwest Atlantic ecosystems. Effects of this community restructuring have cascaded downward from the cownose ray, whose enhanced predation on its bay scallop prey was sufficient to terminate a century-long scallop fishery. Analogous top-down effects may be a predictable consequence of eliminating entire functional groups of predators.

Cascading top-down effects of changing oceanic predator abundances.

1. Top-down control can be an important determinant of ecosystem structure and function, but in oceanic ecosystems, where cascading effects of predator depletions, recoveries, and invasions could be significant, such effects had rarely been demonstrated until recently. 2. Here we synthesize the evidence for oceanic top-down control that has emerged over the last decade, focusing on large, high trophic-level predators inhabiting continental shelves, seas, and the open ocean. 3. In these ecosystems, where controlled manipulations are largely infeasible, pseudo-experimental analyses of predator-prey interactions that treat independent predator populations as replicates, and temporal or spatial contrasts in predator populations and climate as treatments, are increasingly employed to help disentangle predator effects from environmental variation and noise. 4. Substantial reductions in marine mammals, sharks, and piscivorous fishes have led to mesopredator and invertebrate predator increases. Conversely, abundant oceanic predators have suppressed prey abundances. Predation has also inhibited recovery of depleted species, sometimes through predator-prey role reversals. Trophic cascades have been initiated by oceanic predators linking to neritic food webs, but seem inconsistent in the pelagic realm with effects often attenuating at plankton. 5. Top-down control is not uniformly strong in the ocean, and appears contingent on the intensity and nature of perturbations to predator abundances. Predator diversity may dampen cascading effects except where nonselective fisheries deplete entire predator functional groups. In other cases, simultaneous exploitation of predator and prey can inhibit prey responses. Explicit consideration of anthropogenic modifications to oceanic foodwebs should help inform predictions about trophic control. 6. Synthesis and applications. Oceanic top-down control can have important socio-economic, conservation, and management implications as mesopredators and invertebrates assume dominance, and recovery of overexploited predators is impaired. Continued research aimed at integrating across trophic levels is needed to understand and forecast the ecosystem effects of changing oceanic predator abundances, the relative strength of top-down and bottom-up control, and interactions with intensifying anthropogenic stressors such as climate change.

Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

Patterns in marine fish biodiversity can be assessed by quantifying temporal variation in rate of population change, abundance, life history and demography concomitant with long-term reductions in abundance. Based on data for 177 populations (62 species) from four north-temperate oceanic regions (Northeast Atlantic and Pacific, Northwest Atlantic, North mid-Atlantic), 81% of the populations in decline prior to 1992 experienced reductions in their rate of loss thereafter; species whose rate of population decline accelerated after 1992 were predominantly top predators such as Atlantic cod (Gadus morhua), sole (Solea solea) and pelagic sharks. Combining population data across regions and species, marine fish have declined 35% since 1978 and are currently less than 70% of recorded maxima; demersal species are generally at historic lows, pelagic species are generally stable or increasing in abundance. Declines by demersal species have been associated with substantive increases in pelagic species, a pattern consistent with the hypothesis that increases in the latter may be attributable to reduced predation mortality. There is a need to determine the consequences to population growth effected by the reductions in age (21%) and size (13%) at maturity and in mean age (5%) and size (18%) of spawners, concomitant with population decline. We conclude that reductions in the rate of population decline, in the absence of targets for population increase, will be insufficient to effect a recovery of marine fish biodiversity, and that great care must be exercised when interpreting multi-species patterns in abundance. Of fundamental importance is the need to explain the geographical, species-specific and habitat biases that pervade patterns of marine fish recovery and biodiversity.

Trends in the abundance of marine fishes

The Convention on Biological Diversity (CBD) established a target in 2002 to reduce the rate of biodiversity loss by 2010. Using a newly constructed global database for 207 populations (108 species), we examine whether the 2010 target has been met for marine fishes, while accounting for population biomass relative to maximum sustainable yield, BMSY. Although rate of decline has eased for 59% of populations declining before 1992 (a pattern consistent with a literal interpretation of the target), the percentage of populations below BMSY has remained unchanged and the rate of decline has increased among several top predators, many of which are below 0.5BMSY. Combining population trends, a global multi- species index indicates that marine fishes declined 38% between 1970 and 2007. The index has been below BMSY since the mid-1980s and stable since the early 1990s. With the exception of High Seas pelagic fishes and demersal species in the Northeast Pacific and Australia - New Zealand, the multispecies indices are currently below BMSY in many regions. We conclude that the 2010 CBD target represents a weak standard for recovering marine fish biodiversity and that meaningful progress will require population-specific recovery targets and associated time lines for achieving those targets. Resume´ : La Convention sur la diversitebiologique (« CBD ») sest donnee en 2002 comme objectif de reduire le taux de perte de la biodiversiteavant 2010. Utilisant une nouvelle base de donnees globale de 207 populations (108 especes), nous examinons si lobjectif 2010 de la CBD a eteatteint pour les poissons marins, tout en tenant compte de la biomasse des populations relative au rendement maximal durable, BMSY. Malgreune diminution du taux de declin chez 59 % des po- pulations en chute avant 1992 (une tendance qui correspond aune interpretation litterale de lobjectif 2010 de la CBD), le pourcentage des populations sous BMSY sest maintenu constant et le taux de declin sest accelerechez plusieurs des preda- teurs sommitaux, une majoritedesquels sont a un niveau inferieur a 0,5BMSY. Combinant les tendances des populations, un indice global multi-especes montre que les poissons marins ont diminuede 38 % entre 1970 et 2007. Lindice est inferieur aBMSY depuis le milieu des annees 1980 et stable depuis le debut des annees 1990. Avec lexception des populations pela- giques de haute mer et des populations demersales du nord-est du Pacifique et de Nouvelle-Zelande - Australie, les indices multi-especes sont presentement sous BMSY dans plusieurs regions. Nous concluons que lobjectif CBD 2010 represente un faible standard pour recuperer la biodiversitedes poissons marins et quun progresr eel requerra des cibles claires de recu- peration specifiques achacune des populations et soumises ades echeanciers stricts pour atteindre les objectifs vises.

Magnitude and inferred impacts of the seahorse trade in Latin America

Seahorses (genus Hippocampus ) are traded globally for use in traditional medicines, souvenirs and as aquarium fishes. Indications that the trade was expanding geographically in response to increasing demand in consuming nations prompted this first study of the seahorse trade in Latin America. In 2000, over 400 people related to the seahorse trade in Mexico, Central America, Ecuador and Peru were interviewed. Customs data and other trade records from these and five additional countries or regions trading seahorses from Latin America were obtained. Dried seahorses were exported by almost every surveyed country at some point in the 1990s, with Ecuador, Peru and Mexico exporting hundreds of kg per year over multiple years, and the latter two nations both exporting tonnes of seahorses at least twice. The live seahorse trade was confined to Costa Rica, Mexico, Panama and Brazil; the last dominating this trade and exporting several thousand seahorses annually. Substantial declines in seahorse abundance, attributed primarily to incidental catches in shrimp trawl fisheries, were reported consistently by respondents in many regions. These data contributed to an Appendix II listing on the Convention on International Trade in Endangered Species of Wild Fauna and Flora of all seahorses, thereby requiring that the trade be monitored and controlled. Additional conservation measures are needed to address fishing pressure on seahorse populations.

Threatened fishes of the world: Hippocampus erectus Perry, 1810 (Syngnathidae)

D 18-19 (16-20); P 15-16 (14-18); rings 11 + 36 (34-39); base colour ash grey, orange,brown, yellow, red or black, often with a pattern of white lines following contour of neckand sometimes with saddle marks on dorsal surface; tiny white dots on tail. Minimum adultsize 55mm (Lourie et al. 1999), maximum 220mm TL (personal observation, TLD, ILR).Illustration from Ginsburg (1937).

Threatened Fishes of the World: Hippocampus reidi Ginsburg, 1933 (Syngnathidae)

Common names: Cavalo-marinho (Por), longsnout seahorse (Am), slender seahorse (Eng), caballito-de-mar (Spa). Conservation status: Vulnerable according to the IUCN Red List of Threatened Animals (2000) and the List of Threatened Animals of Rio de Janeiro (Mazzoni et al. 2000) and São Paulo States, Brazil (Governo do Estado de São Paulo 1998). Identification: D 17 (16–19), P 16 (15–17), rings: 11+35 (31–39). Often profusely spotted with brown, with numerous tiny white dots especially on tail. May have paler saddles across dorso-lateral surfaces (Lourie et al. 1999). Base colour when live red, orange, yellow, brown, ash grey, black. Skin fronds sometimes present on young (Ginsburg 1937, personal observation). Lourie et al. (1999) noted that skin appendages are usually absent. Illustration from Ginsburg (op. cit.). Distribution: From Cape Hatteras, United States to Rio de Janeiro, Brazil and Gulf of Mexico (Lourie et al. 1999). Abundance: No published information is available on the abundance of H. reidi, but a by catch study and trade research suggests that it is less abundant than H. erectus in the Gulf of Mexico and Central America (JKB, unpublished data). Collection records and indirect evidence from trade research suggest that H. reidi is more abundant than H. erectus in Brazil, where it has been found singly or in small groups (up to 4 individuals) (TLD, ILR, personal observation). Vari (1982) mentioned that the species can be found at depths between 15 and 55 m. In Brazil it has been found close to the water surface, at a depth of about 10 cm (TLD, ILR, personal observation). Habitat and ecology: Known to occur in association with mangrove roots (mostly Rhizophora mangle and Avicennia sp.), seagrass (Thalassia testudinum, Halophila sp., Halodule wrightii), macroalgae (Caulerpa spp.), oysters, cnidarians (Carijoa sp.), sponges and tunicates (Ascidia spp.), usually using the tail to coil around these substrates that are used as holdfasts. Also found in association with man-made structures in estuaries. Home range is between 6 and 20 m2 with a maximum observed displacement of 143 m . In Brazil it has been found in salinity of 45‰ (TLD, ILR, personal observation). Reproduction: There is no published information on the reproduction of H. reidi based on studies carried out in the wild. A laboratory study indicates that the breeding season extends to more than eight months with a gestation period of two weeks, varying with temperature; egg diameter 1.2 mm, brood size about 1000, with one male producing 1536 young; young approximately 7 mm at release (Vincent 1990). Silveira (2000) observed that males remate with the same female about two days after releasing the young. Threats: Collection for use as aquarium fishes, folk medicine, souvenirs and for religious purposes, by catch in shrimp trawl fisheries in U.S., Mexico and Central America (some retained for export to Asia for the traditional Chinese medicine trade). Conservation recommendations: Population parameters and ecology of H. reidi should be studied in the wild; live and dried trade should be quantified and its effects on wild populations evaluated; further taxonomic research should be undertaken to determine the status of populations throughout the species’ range, and suitable sanctuary zones should be established, where fishing is prohibited or strictly regulated. Remarks: The longsnout seahorse may be regarded as a flagship species that can help to promote marine conservation. This fact, together with its unique reproduction, provides important reasons for its conservation.