Marine mammals may be accidentally captured in purse seines. They may also become entangled in longlines or or hooked on them, e.g., false killer whales in the Hawaii-based deep-set longline fishery. In the tropical tuna purse-seine fishery, species such as baleen whales or dolphins (as well the whale shark Rhincodon typus), may serve as sighting cues by purse-seine fishermen for the presence of tuna schools at the surface of the sea and/or may be caught accidentally when fishing for the targeted species [1].
Successful techniques to release marine mammals from purse seine nets have been employed for some time, e.g., the backdown procedure and Medina panel, and there have been advances in techniques for safe handling and release of megafauna from purse seines [2,3]. Progress in the development of dynamic spatial fishery management strategies will help fishers to avoid interactions in the first place. For example, a recent study identified the principal environmental variables influencing the co-occurrence between baleen whales, whale sharks and tuna purse-seine fisheries [1]. Fishing area closures are utilised in the interim. 'Weak' circle hooks and strong branchlines are required in the Hawaii-based deep-set and shallow-set longline fisheries (see NOAA's Whale link below). They can reduce bycatch (but not depredation), though post-interaction mortality is unknown.
SeaLlifeBase is a source of biological and distribution data for marine mammal species. FAO's guide to the Marine Mammals of the World provides species identification and distribution information. Locate handy Species ID guides here. NOAA's 'Find a Species - Dolphins & Porpoises' and 'Whales' has information on protection status, biology and population status, distribution, threats, conservation measures and research.
References
- Escalle, L., Pennino, M.G., Gaertner, D., Chavance, P., Delgado de Molina, A., Demarcq, H., Romanov, E., and Merigot, B. 2016. Environmental factors and megafauna spatio-temporal co-occurrence with purse-seine fisheries. Fisheries Oceanography 25(4): 433–447. doi:10.1111/fog.12163.
- Escalle, L., Murua, H., Amande, J.M., Arregui, I., Chavance, P., Delgado de Molina, A., Gaertner, D., Fraile, I., Filmalter, J.D., Santiago, J., Forget, F., Arrizabalaga, H., Dagorn, L., and Merigot, B. 2016. Post-capture survival of whale sharks encircled in tuna purse-seine nets: tagging and safe release methods. Aquatic Conservation: Marine and Freshwater Ecosystems 26(4): 782–789. doi:10.1002/aqc.2662.
- Poisson, F., Vernet, A.L., Seret, B., and Dagorn, L. 2012. Good practices to reduce the mortality of sharks and rays caught incidentally by the tropical tuna purse seiners. EU FP7, EBFMtuna-2012 Montpellier, France.

Species
3-Alpha Code | Name | Scientific Name |
---|---|---|
BBW | BEAKED WHALE, BLAINVILLE’S | Mesoplodon densirostris |
BCW | BEAKED WHALE, CUVIER'S | Ziphius cavirostris |
BEW | BEAKED WHALE, BAIRD'S | Berardius bairdii |
BLW | BLUE WHALE | Balaenoptera musculus |
BRW | BRIDE'S WHALE | Balaenoptera Edeni |
CSL | SEA LION, CALIFORNIA | Zalophus californianus |
DBO | BOTTLENOSE DOLPHIN | Tursiops truncatus |
DBZ | INDO-PACIFIC BOTTLENOSE DOLPHIN | Tursiops aduncus |
DCO | COMMON DOLPHIN | Delphinus delphis |
DCZ | LONG-BEAKED COMMON DOLPHIN | Delphinus capensis |
DDU | DUSKY DOLPHIN | Lagenorhynchus obscurus |
DPN | DOLPHIN, SPOTTED | Stenella attenuata |
DRR | RISSO'S DOLPHIN | Grampus griseus |
DSI | SPINNER DOLPHIN | Stenella longirostris |
DSP | SPOTTED DOLPHINS | Stenella spp. |
DST | STRIPED DOLPHIN | Stenella coeruleoalba |
DWP | DOLPHIN, PAC. WHITE-SIDED | Lagenorhynchus obliquidens |
DWW | DWARF SPERM WHALE | Kogia simus |
FAW | FALSE KILLER WHALE | Pseudorca crassidens |
FRD | DOLPHIN, FRASER'S | Lagenodelphis hosei |
GRW | GRAY WHALE | Eschrichtius robustus |
HUW | HUMPBACK WHALE | Megaptera novaeangliae |
KPW | PYGMY KILLER WHALE | Feresa attenuata |
MAM | MARINE MAMMAL (UNIDENTIFIED) | Mammalia |
MEW | MELON-HEADED WHALE | Peponocephala electra |
MIW | MINKE WHALE | Balaenoptera acutorostrata |
ODN | TOOTHED WHALES NEI (BLACKFISH) | Odontoceti |
PDA | PORPOISE, DALL'S | Phocoenoides dalli |
PHR | PORPOISE, HARBOR | Phocoena phocoena |
PIW | Long-finned pilot whale | Globicephala melas |
PYW | PYGMY SPERM WHALE | Kogia breviceps |
RNW | DOLPHIN, N. RIGHT WHALE | Lissodelphis borealis |
RTD | DOLPHIN, ROUGH-TOOTHED | Steno bredanensis |
SEA | NEW ZEALAND FUR SEAL | Arctocephalus forsteri |
SEC | SEAL, HARBOR | Phoca vitulina |
SEK | Australian Fur Seal | Arctocephalus pusillus |
SEN | FUR SEAL, NORTHERN | Callorhinus ursinus |
SGF | FUR SEAL, GUADALUPE | Arctocephalus townsendi |
SHW | SHORT-FINNED PILOT WHALE | Globicephala macrorhynchus |
SIW | SEI WHALE | Balaenoptera borealis |
SMH | SEAL, HAWAIIAN MONK | Monachus schauinslandi |
SNP | SEAL, NORTHERN ELEPHANT | Mirounga angustirostris |
SPW | SPERM WHALE | Physeter macrocephalus |
SSL | SEA LION, STELLER | Eumetopias jubatus |
SXX | SEALS | Otariidae, phocidae |
TGW | GINKGO-TOOTHED BEAKED WHALE | MesoplodonGinkgodens |
WLE | WHALE (UNIDENTIFIED) | Cetacea |