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In press) Following strict regulations to reduce kills every year unsustainable numbers of endan-
bycatch, dolphin mortality in Pacific tuna nets gered baiji (Perrin et al. 1989).
has substantially decreased in recent years. How- Longlines are commonly used in the Mediter-
ever, the past and present impact may be signifi- ranean for catching tuna, albacore, swordfish and
cantly underestimated because of unobserved a number of other fish (Di Natale 1990). Al-
deaths of nursing calves due to separation from though a few cases of incidental catches of ceta-
their mothers during fishing (Archer et al. 2001). ceans have been reported, clear evidence is often
Fishing with purse seines aimed at tuna ap- missing because cetaceans can be released alive
pears to be scarcely practiced in the Mediterra- at sea by fishermen. Reports of cetaceans caught
nean, where purse seining appears to be mostly by longlines include a few striped dolphins,
targeted to small epipelagic schooling fish. In the common bottlenose dolphins, Risso's dolphins,
Italian seas, Di Natale and Notarbartolo di Sciara false killer whales and sperm whales taken in It-
(1994) reported only ten tuna nets being used, for aly and Spain (Di Natale and Mangano 1983, Di
a total of 1,000 fishermen involved and a fishing Natale 1990, Mussi et al. 1998). In all these
period of 60 days per year. Bycatch in purse cases, the gear was a surface drifting longline for
seines would mainly affect small odontocetes swordfish.
such as striped dolphins, bottlenose dolphins and In the Italian seas, most reports of entangle-
common dolphins (Di Natale 1983a, 1983b, ment in longlines have involved small Odonto-
1990, UNEP/IUCN 1994). Rare reports exist of cetes, particularly striped dolphins, but docu-
cetaceans bycaught in tuna purse-seine in the mented cases exist for Risso’s dolphins (Catald-
Mediterranean (e.g., Magnaghi and Podestà ini and Bello 1987), common bottlenose dol-
1987). Overall, the impact of these nets on Medi- phins, long-finned pilot whales, sperm whales,
terranean cetaceans is commonly considered to and a young fin whale (Di Natale 1990,
be negligible (Di Natale and Notarbartolo di Sci- UNEP/IUCN 1994, Centro Studi Cetacei
ara 1994). However, reliable information is 1987÷1998, Mussi et al. 1998). Some individu-
completely lacking, and thus an accurate assess- als (striped dolphins, Risso’s dolphins and com-
ment of the impact of tuna purse seine fishing on mon bottlenose dolphins), have been found
cetaceans in the Mediterranean is presently im- stranded with hooks in their mouths, or with fish-
possible. ing lines in their larynx, suggesting that in some
cases these animals may try to feed on bait or
Entrapment in longlines. Longlines consist of a hooked fish. Mussi et al. (1998) reported interac-
series of baited hooks attached to a long, horizon- tions with fisheries using illuminated handlines
tal line by short connecting lines. This type of for squids. These involved small groups of
fishing gear can be configured to take a wide va- striped dolphins, Risso's dolphins, and long-
riety of fish, from small, bottom-dwelling species finned pilot whales waiting near the fishing boats
to large pelagic species such as swordfish, tuna until the light had attracted a great number of
and sharks. The use of different hook sizes and squids. Cetaceans would then take profit of the
fishing depths allows fishermen considerable higher prey density and forage near the fishing
flexibility in their choice of target species. In boats. However, no cetacean bycatch was re-
many areas longlines are important components ported during these interactions.
of coastal and pelagic fisheries (Read 1996). Comprehensive studies on the potential im-
Cetaceans may get entangled in the line fila- pact of longlines on cetaceans in the Mediterra-
ments or in other parts of the gear, or get hooked nean have never been conducted. However, this
(Green et al. 1991, Read 1996). In some areas seems likely to represent a minor threat in the ba-
around the world, mortality related to longline sin.
fisheries may be significant (Crespo et al. 1997,
Reeves et al., in prep.). For instance, in the Entrapment in discarded or abandoned nets.
southern U.S., short-finned pilot whales can get Nets that remain entangled on the sea floor, or
entangled in longline fisheries for swordfish and that are damaged or worn out, may be discarded
tuna; most entangled animals are released alive, or abandoned by fishermen at sea. Gillnets,
but it is not known what effects the hooks and/or driftnets or other fishing gear may also be broken
entanglement may have on their survival after re- or dispersed by storms. These nets can then con-
lease (Read 1996). In the Yangtze River, China, tinue to catch and kill cetaceans and other marine
a bottom longline fishery called 'rolling hooks' animals for decades, until the net filaments com-

Cetaceans of the Mediterranean and Black Seas – 9.8