Anderson, Charles,Herrera, Miguel,Ilangakoon, Anoukchika,Koya, KM,Moazzam, M,Mustika, Putu L,Sutaria, Dipani N Cetacean bycatch in Indian Ocean tuna gillnet fisheries Journal Article Endangered Species Research, 41 (292), pp. 39-53, 2020, ISSN: 1863-5407. Abstract | Links | BibTeX | Keywords: Bycatch, Estimates, Extrapolation, Gill net, gillnet, Indian Ocean, mortality, Observer programmes, Oman, Pakistan, Sri Lanka, Trends, tuna fishery @article{, title = {Cetacean bycatch in Indian Ocean tuna gillnet fisheries}, author = {Anderson, Charles,Herrera, Miguel,Ilangakoon, Anoukchika,Koya, KM,Moazzam, M,Mustika, Putu L,Sutaria, Dipani N}, url = {https://www.int-res.com/prepress/n01008.html}, doi = {https://doi.org/10.3354/esr01008}, issn = {1863-5407}, year = {2020}, date = {2020-01-01}, journal = {Endangered Species Research}, volume = {41}, number = {292}, pages = {39-53}, abstract = {Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combine published results from 10 bycatch sampling programmes (1981–2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100,000 individuals yr–1 during 2004–2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, nor of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean. }, keywords = {Bycatch, Estimates, Extrapolation, Gill net, gillnet, Indian Ocean, mortality, Observer programmes, Oman, Pakistan, Sri Lanka, Trends, tuna fishery}, pubstate = {published}, tppubtype = {article} } Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combine published results from 10 bycatch sampling programmes (1981–2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100,000 individuals yr–1 during 2004–2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, nor of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean. |
Caron,D.A.,Dennett,M.R. Phytoplankton growth and mortality during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea Journal Article Deep-Sea Research Part II, 46 (63), pp. 1665-1690, 1999. Abstract | BibTeX | Keywords: Arabian Sea, chlorophyll, growth, mortality, Oceanic, trend, Trends @article{, title = {Phytoplankton growth and mortality during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea}, author = {Caron,D.A.,Dennett,M.R.}, year = {1999}, date = {1999-01-01}, journal = {Deep-Sea Research Part II}, volume = {46}, number = {63}, pages = {1665-1690}, abstract = {Phytoplankton growth rates and mortality rates were experimentally examined at eight stations in the Arabian Sea along the U.S. JGOFS cruise track during the 1995 Northeast Monsoon (January) and Spring Intermonsoon (March-April). Instantaneous growth rates averaged over an entire cruise were approximately twice as high during the NE Monsoon than during the Spring Intermonsoon period (overall averages of 0.84 ñ 0.29 (s.d.) versus 0.44 ñ 0.19 d-1). Average herbivore grazing (mortality) rates, however, were quite similar for the two seasons (overall averages of 0.35 ñ 0.18 and 0.30 ñ 0.17 d-1 for the NE Monsoon and Spring Intermonsoon, respectively). The absolute amounts of phytoplankton biomass consumed during each season also were similar (29 and 25% of standing stock consumed d-1 for the January and March-April cruises, respectively), as were the geographical trends of this removal. These seasonal trends in growth and removal rates resulted in net phytoplankton growth rates that were considerably higher during the January cruise (0.48 d-1) than during the March-April cruise (0.14 d-1). That is, phytoplankton production was more closely balanced during the Spring Intermonsoon season (87% of daily primary production consumed) relative to the NE Monsoon season (49% of daily primary production consumed). Station-to-station variability was high for rate measurements during either cruise. Nevertheless, there was a clear onshore-offshore trend in the absolute rate of removal of phytoplankton biomass (æg chlorophyll consumed l-1 d-1) during both cruises. Coastal stations had removal rates that were typically 2-4 times higher than removal rates at oceanic stations.}, keywords = {Arabian Sea, chlorophyll, growth, mortality, Oceanic, trend, Trends}, pubstate = {published}, tppubtype = {article} } Phytoplankton growth rates and mortality rates were experimentally examined at eight stations in the Arabian Sea along the U.S. JGOFS cruise track during the 1995 Northeast Monsoon (January) and Spring Intermonsoon (March-April). Instantaneous growth rates averaged over an entire cruise were approximately twice as high during the NE Monsoon than during the Spring Intermonsoon period (overall averages of 0.84 ñ 0.29 (s.d.) versus 0.44 ñ 0.19 d-1). Average herbivore grazing (mortality) rates, however, were quite similar for the two seasons (overall averages of 0.35 ñ 0.18 and 0.30 ñ 0.17 d-1 for the NE Monsoon and Spring Intermonsoon, respectively). The absolute amounts of phytoplankton biomass consumed during each season also were similar (29 and 25% of standing stock consumed d-1 for the January and March-April cruises, respectively), as were the geographical trends of this removal. These seasonal trends in growth and removal rates resulted in net phytoplankton growth rates that were considerably higher during the January cruise (0.48 d-1) than during the March-April cruise (0.14 d-1). That is, phytoplankton production was more closely balanced during the Spring Intermonsoon season (87% of daily primary production consumed) relative to the NE Monsoon season (49% of daily primary production consumed). Station-to-station variability was high for rate measurements during either cruise. Nevertheless, there was a clear onshore-offshore trend in the absolute rate of removal of phytoplankton biomass (æg chlorophyll consumed l-1 d-1) during both cruises. Coastal stations had removal rates that were typically 2-4 times higher than removal rates at oceanic stations. |
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Cetacean bycatch in Indian Ocean tuna gillnet fisheries Journal Article Endangered Species Research, 41 (292), pp. 39-53, 2020, ISSN: 1863-5407. |
Phytoplankton growth and mortality during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea Journal Article Deep-Sea Research Part II, 46 (63), pp. 1665-1690, 1999. |