Cetaceans at risk Cetacean bycatch

1 cetaceans @ risk

1.1 atlantic humpback dolphins
1.2 baleen whales
1.3 burmeister’s porpoises
1.4 commerson’s dolphins
1.5 la plata dolphins
1.6 harbour porpoises
1.7 hector s , maui s dolphins
1.8 indo-pacific humpback , bottlenose dolphins
1.9 irrawaddy dolphins
1.10 spinner , fraser’s dolphins
1.11 yangtze river dolphins , finless porpoises
1.12 vaquita

cetaceans @ risk

bycatch recognized primary threat cetaceans. following cetaceans @ high risk entanglement in gillnets:

atlantic humpback dolphins

the atlantic humpback dolphin (sousa teuszii) endemic west africa. several stocks have been identified numbers ranging tens few hundred. abundance estimates lacking. gaps in species range , hence distribution evident. bycatch documented in few west african countries. surveys , evaluations need conducted determine presence/ absence of humpback dolphins in historical range. conservation measures need implemented save species. because many people live off sea, not feasible have complete gillnet closures. areas may designated off-limits gillnet fisheries. eco-tourism may implemented because of high species diversity.

baleen whales

north atlantic right whale mother , calf.

baleen whales, mysticeti, taken in gill-nets , in fisheries use vertical lines mark traps , pots. large cetaceans such humpback , right whales may carry off gear after entanglement. explains large scars borne whales along u.s. atlantic coast. analyses show 50-70% of gulf of maine humpback whales, megaptera novaeangliae, , north atlantic right whale, eubalaena glacialis, have been entangled @ least once in lifetime. north atlantic right whale 1 of endangered large cetaceans , 300-350 individuals remain. minke whales, balaenoptera acutorostrata, @ risk.

burmeister’s porpoises

the burmeister s porpoise (phocoena spinipinnis) 1 of 3 cetaceans bycaught in peru , chile. several thousand porpoises caught each year in peru alone. bycatch frequent occurrence species because of inability detect them in water. surveys have shown bycatch remains concern in area today , unknown whether or not population declining. data, conservation measures , awareness lacking. these porpoises cryptic making surveying challenge . difficult estimate bycatch because sale of porpoise meat no longer available @ markets.

commerson’s dolphins

a commerson s dolphin in aquarium.

the expanding trawl fisheries devastated commerson s dolphin (cephalorhynchus commersonii) populations in patagonia. trawl fisheries expanded twenty years until crashed in 1997. pelagic squid fisheries took on use pelagic trawls harmful dusky, short-beaked common dolphins, , commerson’s dolphins. there approximately 21,000 commerson’s dolphins remaining today. 2 stocks have been identified in population genetic information , bycatch levels unknown. anchovy fisheries expanding, imperative assess commerson’s dolphin population before these fisheries grow. seasonal operation of in-shore gillnet fisheries known involve bycatch of cetaceans. presently, there no known estimates of gillnet bycatch. bycatch problem in argentina political in nature. improvements in fishing technology, awareness, , large scale survey of commerson’s dolphin populations , impact of bycatch essential.

la plata dolphins

the la plata or franciscana dolphin (pontoporia blainvillei) threatened small cetacean in southwest atlantic ocean due bycatch. found in coastal waters of argentina, brazil, , uruguay. species has been divided 4 ranges (fmu’s: franciscana management units) management , conservation purposes. these populations genetically different. mortality rates 1.6% fmu 4 , 3.3% fmu 3 unknown whether these estimates accurate. aerial surveys have proven inconclusive far population numbers of franciscanas. rectify situation, more surveys needed political commitment, awareness campaigns , bycatch mitigation techniques.

harbour porpoises

there substantial incidental catches in fishing operations. often, harbour porpoise (phocoena phocoena) killed incidental by-catch (10, 11, 12). gillnets pose serious threat harbour porpoise extremely susceptible entanglement. study caswell et al. in western north atlantic combined mean annual rate of increase of harbour porpoise uncertainty of incidental mortality , population size. found incidental mortality exceeds critical values , therefore by-catch significant threat harbour porpoise. harbour porpoises become entangled in nets due inability detect nets before collision. in 2001, 80 harbour porpoises killed in salmon gillnet fisheries in british columbia, canada.

hector s , maui s dolphins

hector s dolphins have unique rounded dorsal fin.

in new zealand, these dolphins have high rate of entanglement. hector s dolphin (cephalorhynchus hectori) endemic coastal waters new zealand , there 7,400 in abundance. small population of hector’s dolphins isolated on west coast of island , have been declared subspecies called maui s dolphin. maui s dolphins (cephalofhynchus hectori maui) caught in set nets , pair trawlers resulting in less 100 left in wild. protection, section of dolphin’s range on west coast has been closed gillnet fisheries.

indo-pacific humpback , bottlenose dolphins

drift , bottom-set gillnets biggest conservation threat these dolphins in indian ocean. there have been assessments in areas, such zanzibar. hunting, until 1996, reduced population , contributed decline. hunting has been replaced eco-tourism. estimated in 2001 there 161 bottlenose dolphins (tursiops aduncus) , 71 indo-pacific humpback dolphin (sousa chinensis) left based on photo-identification mark-recapture techniques. study on bycatch revealed on 160 incidences of bycatch since 2000. approximately 30% of bycatch in drift , bottom-set gillnets. mortality 8% , 5.6% bottlenose , humpback dolphins respectively . mitigation of bycatch imperative these species , eco-tourism.

irrawaddy dolphins

based on survey in 2001, fewer 70 irrawaddy dolphins (orcaella brevirostris) left in upper region of malampaya sound in philippines , 69 individuals in mekong river. have been severely impacted lift nets, , crab gear , critically endangered. estimated mortality bycatch may greater 4.5% in malampaya sound , 5.8% in mekong river. population declining dramatically. current bycatch levels unsustainable , bycatch reduction measures long-term systematic monitoring urgently required. elimination of gillnets areas of high use needed , economic incentives need provided local people.

spinner , fraser’s dolphins

spinner dolphins.

in philippines, tuna driftnet fisheries have substantial impact on populations. 1 tuna fishery alone kills 400 spinner dolphin (stenella longirostris) , fraser s dolphins (lagenodelphis hosei) each year. round-haul nets greater concern bycatch of 3000 dolphins per year. dolphins bycaught end shark bait longline fisheries. there not enough data conclude total bycatch philippines. initial assessment indicates bycatch not sustainable. monitoring of dolphin populations , fisheries urgently needed.

yangtze river dolphins , finless porpoises

illustration of baiji dolphin.

the yangtze river or baiji dolphin (lipotes vexillifer) endangered cetacean , found in yangtze river, china. survey conducted in 1997 found thirteen dolphins. yangtze river finless porpoise (neophocaena phocaenoides asiaeorientalis) lives in yangtze river. abundance has declined , there fewer 2000 dolphins left. may due, in part, construction of 3 gorges dam covers significant amount of dolphin’s habitat. both species subject entanglement in gillnets.

vaquita

the vaquita (phocoena sinus) highly endangered , endemic upper gulf of california, mexico. killed in both gillnets , trawl nets commercial , artisanal fishing. there presently less 100 vaquitas left in gulf of california.