histius bmsiliensis, A SQUALOID SHARK, THE PROBABLE CAUSE OF 

 CRATER WOUNDS ON FISHES AND CETACEANS 



EVERET C. Jones' 



ABSTRACT 



Evidence is presented that bites inflicted by the small squaloid shark, Isistius brasiliensis (Quoy and 

 Gaimard) , are the causes of crater wounds, crescentic wounds, and related scars on large pelagic 

 fishes and cetaceans. This evidence consists of a ci-escentic "wound" experimentally produced on the 

 side of a dead fish by a living Isistiu.s; specialized morphology of the shark's basihyoid cartilage and 

 coracohyoideus muscles, lips, labial cartilages, and spiracles, that, together, enable the shark to form 

 an oral vacuum on a smooth surface; an experiment in which a living Isistin.'i formed such a vacuum; 

 specialized morphology and arrangement of the mandibular teeth ; close agreement between the range 

 of reported wound widths and the estimated range of bite widths of Isif^titis; agreement between the 

 geographical ranges of Isistius and those fishes and cetaceans which bear crater wounds; and, finally, 

 the presence in Isistius stomachs of hemispheroidal plugs of fish flesh. Speculation on the circumstances 

 that may enable a small, slow shark to make contact with large, swift fishes and cetaceans is included. 

 Isistius apparently qualifies as a temporary parasite. 



Probably the earliest account of the existence 

 of small, round or oval, scooped-out wounds on 

 the sides of large pelagic fishes is contained in 

 an ancient legend of Samoa (A. Utu, personal 

 communication), which states that atu (skip- 

 jack tuna, S^^f/ii/z^/nts /*e^a>H/s (Linnaeus)) en- 

 tered Palauli Bay, and, upon approaching the 

 beach, left small round pieces of their flesh as 

 gifts to Tautunu. chief of that community. Evi- 

 dence of this sacrifice was found by the people 

 who caught the atu and observed fresh, round 

 wounds on their sides. 



This legend provides one of many explanations 

 that have been advanced regarding the causes 

 of such wounds on large pelagic fishes as well 

 as on whales and porpoises. This paper jjresents 

 evidence that many crater wounds, crescentic 

 wounds, and the resulting scars on pelagic fishes 

 (Figure 1), and open pit wounds and resulting 

 scars on cetaceans are the results of bites in- 

 flicted by the small squaloid shark, Isistius bra- 

 siliensis (Quoy and Gaimard). (A second spe- 

 cies, Isistiits phitodns, was described by Garrick 

 and Springer (1964) from the Gulf of Mexico. 

 Although nothing is known of the behavior of 



' National Marine Fisheries Service, Hawaii Area 

 Fishery Research Center, Honolulu, Hawaii 96812. 



Manuscript accepted June 1971. 



FISHERY BULLETIN: VOL. 69, NO. 4. 



this species, which is based on one specimen, 

 it is probable that its feeding habits are similar 

 to those of I. brasiliensis.) 



Such wounds on fishes have been reported by 

 Nemoto (1955), Iversen (1959), Guitart M. 

 (1964), Klawe (1966), Bane (1969), and Ma- 

 chado Cruz (1969). The literature on open pit 

 wounds and related scars on cetaceans is much 

 more extensive, apparentl.v beginning with the 

 work of Collett ( 1886) . Mackintosh and Wheel- 

 er (1929) and van Utrecht (1959) presented 

 thorough discussions of these wounds and proba- 

 ble causes, and summarized the previous litera- 

 ture. Nemoto (1955) noted that some of the 

 wounds observed on whales are similar to and 

 Ijrobably have a common origin with those on 

 fishes. He further stated that a cause other than 

 lamprey attacks, the most commonly advocated 

 agent, must be found to account for crescent- 

 shaped scars and open pit wounds on cetaceans 

 and fishes. 



It was not always jjossible for me to determine 

 whether published photograijhs and descriptions 

 were of wounds and scars of the types which I 

 attribute to Isistius bites. I have never seen 

 wounds known to have been produced by lam- 

 preys and therefore cannot comment with any 



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