Full report - Conservation Gateway

Chapter 9 - Large Pelagic Fishhave documented climate change impacts (see reviews inUNEP/CMS 2006; Hobday et al. 2006), but there areseveral programs currently collecting information on climatechange, including GLOBEC’s Climate Impacts onOceanic Top Predators (CLIOTOP) program (Mauryand Lehodey 2005). Likely impacts include sea surfacetemperature changes and corresponding changes in thefood web, wind forcing changes, acidification, changesin prey populations, and increased pollution at the seasurface.Changes in ocean temperature in time and position couldaffect the distribution of pelagic species. On the UnitedStates east and west coast, sea surface temperature hasincreased, causing shifts in timing of zooplankton, whichaffects the entire food web (see Moran 2008; ScrippsInstitute of Oceanography 1995). Wind also indirectlyimpacts pelagic species by mixing the surface waters (Curyand Roy 1989). If significant changes to wind forcing dooccur, this could impact coastal pelagic systems (Bakunand Weeks 2004). The productivity of pelagic systemscould change, depending on the relative balance of nutrients,light, and timing of phytoplankton production.There is notable concern about the pH changes occurringin the open ocean. While it is expected to be small comparedto benthic habitats, acidification could impact lowertrophic levels. The scalloped hammerhead, sand tiger, andsandbar shark – all of whom feed to some degree on benthicinvertebrates - could be impacted. Other, fast-swimming,high metabolic species such as the tuna and billfishcould be affected by changes to their metabolism (Pörtnerand Farrell 2008). These animals are at the edge of physiologicextremes in their energy and oxygen needs. Changein prey populations will also potentially affect these species.CLIOTOP is analyzing the role of climate change onloligo squid, a key prey item for tunas and billfishes (Pecland Jackson 2006). Squid are expected to be very sensitiveto climate change, particularly increased temperature.They are expected to respond extremely rapidly, and maybe good indicators for climatic impacts.In summary, the individual and combined threatsof global climate change described above could haveboth subtle and dramatic impacts to pelagic fishpopulations. While the science regarding the natureand likelihood of these impacts is advancing rapidly,substantial uncertainty remains. In the face of suchuncertainty, an extra precautionary approach is indicatedwhen managers must make key decisions regardingabatement of known threats such as overfishing,bycatch, and nearshore habitat loss and degradation.Conservation measures that abate non-climatechange related impacts will help to increase resiliencyof populations while explicit climate change adaptivemanagement strategies are still being developed andtested.Management andConservationRegulatory AuthoritiesUnlike the other fish species, these animals are not regulatedby the regional fisheries management councils. Since1992, within the United States Exclusive Economic Zone(EEZ), Atlantic highly migratory species, including tuna,swordfish, billfish (the two marlin species) and sharksare managed by NMFS HMS, under the dual authorityof the Magnuson-Stevens Fishery Conservation andManagement Act and the Atlantic Tunas Convention Act.NAFO is a regional, non-regulatory body. Its objectiveis regional cooperation and consultation on fisheries ofthe NAFO Convention Area of the Northwest Atlantic,including swordfish, porbeagle, shortfin mako, and largesharks; the NAFO Convention does not apply to tunas ormarlin.Because of the circumglobal distribution of many of thespecies and the fact that the species are often found outsideof exclusive economic zones, management requiresinternational cooperation through ICCAT. Note thatICCAT only regulates Atlantic tunas, swordfish and billfish;it does not regulate Atlantic sharks. If ICCAT makesa management recommendation, the United States mustNorthwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 9-27