The Tasmantid seamount chain: geomorphology, benthic biodiversity and fishing history

[摘要] This report summarises selected physical and biological data for the Tasmantid seamount chain to inform two current marine conservation planning processes: marine planning by the DSEWPaC for the Temperate East (TE) marine region, and an AFMA management strategy that aims to reduce fishing impacts on, and support recovery of, Harrisson’s Dogfish, a species being considered for threatened species listing.Pre-existing knowledge of benthic ecosystems on the Tasmantid seamount chain is sparse, and/ or un-summarised, and has, for example, precluded indicator analysis, meso-scale bioregionalisation and seascape analysis in support of conservation planning.Data on historical fishing patterns and the ecology of Harrisson’s Dogfish were also incomplete for fishery management planning. Our summaries include recently collected information from ongoing projects (particularly Williams et al. 2012a), and other un-summarised data (e.g. museum collections), for 11 individual seamounts that occupy shelf and upper/ mid-slope depths (2,000 m).This is the depth range of greatest importance for management consideration because it is where benthic biodiversity is expected to be greatest, and where fishing impacts are concentrated (Williams et al., 2009).The broad patterns in our summaries show that:- individual seamounts vary greatly in their size (area) in shelf and upper/mid-slope depths.- Taupo Seamount supports a diverse and dense invertebrate megafauna, and abundant sharks, in shelf and upper slope depths. - the museum collections from the seamount chain represent a limited knowledge of the biodiversity present, including little species-level information (identities, distributions, abundances).- a high diversity of demersal fishes is recorded in commercial logbooks and by fishery observers. - the distributions and abundances of commercial fishery species (e.g. Blue-eye Trevalla) or prospectively commercial species (e.g. Alfonsino) differ markedly between seamounts.- there have been highly variable patterns of historical commercial bottom fishing effort on individual seamounts- records of invertebrate fishery bycatch are few but these indicate impacts have included the removal of epibenthic biodiversity, including deepwater octocorals and crinoids that potentially represent vulnerable marine ecosystemsInformation summarised for the 8 primary seamounts (Table 4.1) shows feature size and area for shelf and upper/ mid-slope depths (indicating the extent of prospective fishing areas and individual depth ranges or biomes); the degree of historical bottom fishing by gear type (giving insights into historical fishing importance and impacts on benthic habitat); and the relative importance of each seamount for selected commercial and ecologically prominent demersal fishes.This report does not attempt to provide suggestions for future management actions, or to evaluate current or proposed management measures. Rather, the summary data are intended to provide insights to inform the management processes, including DSEWPaC’s considerations for IUCN zoning and fishery risk assessment, and AFMA’s consideration of potential fishery closures. Further analysis could be undertaken to support the integration of measures to conserve biodiversity with ecosystem based fishery management (e.g. for a fishing risk assessment).The paucity of biodiversity data demonstrates the need for a greater degree of biodiversity inventory to validate the surrogates used to identify conservation values.There is some scope for scientifically directed sampling from fishing vessel platforms to contribute to this, e.g. through e-monitoring, sensor deployments, tagging, and biological sampling, that could be considered during the development of management measures.

[发布日期] 2012-12-20 [发布机构] CSIRO Marine and Atmospheric Research

[效力级别] Biological Oceanography [学科分类] 地球科学(综合)