NOTES 



OBSERVATIONS ON A WHITE-SIDED 



DOLPHIN, LAGEMORHYNCHUS ACUTUS, 



PROBABLY KILLED IN GILL NETS IN 



THE GULF OF MAINE 



On 20 July 1976, a white-sided dolphin, Lageno- 

 rhynchus acutus, was observed floating with its 

 beak out of the water on Jeffreys Ledge, Maine 

 (lat. 43°09'N, long. 70°04'W). The 201-cm long 

 female weighed 113.2 kg and was freshly dead, 

 still bleeding freely from symmetrical injuries to 

 the left and right sides of both the upper and lower 

 jaws and the flippers. The lungs contained foamy 

 materials and were mottled white, indicating 

 drowning as the immediate cause of death. Many 

 gill nets were present in the area, and the sym- 

 metrical nature of the injuries indicated that the 

 animal had become entangled in the mesh, 

 drowned, and perhaps been freed or discarded dur- 

 ing hauling of the net. A humpback whale, 

 Megaptera novaengliae, was entangled in a gill net 

 for 2 h before freeing itself on the same day in the 

 same general area. 



Gross autopsy revealed several cysts in the ab- 

 dominal muscles of the lower left side and a 5 cm x 

 7.5 cm yellow, pussy abscess 15 cm anterior and 

 dorsal to the right mammary gland, perhaps 

 caused by a bladderworm stage (plerocercoid) of 

 Monorygma grimaldi (Geraci et al.M. No other 

 parasites were found, although all major organs 

 except the brain were inspected. Tissue and organ 

 weights are shown in Table 1. The length and 



'Geraci, G., S. A. Testaverde, D. J. St. Aubin, and T. H. Loop. 

 1976. A mass stranding of the Atlantic white-sided dolphin, 

 Lagenorhynchus acutus: a study into pathobiology and life his- 

 tory. Unpubl. manuscr., 166 p. submitted to Marine Mammal 

 Commission by New England Aquarium, Boston. 



Table l. — Tissue and organ weights of a Lagenorhynchus 

 acutus from Jeffreys Ledge, Maine. Weights not corrected for 

 blood loss. 



weight of this animal fit well on a regression line 

 developed for this species (Geraci et al. see foot- 

 note 1). From a length-age relationship (Geraci et 

 al. see footnote 1), it is likely that this female was 

 between 2y2 and 3 yr old, and was immature. 



The stomach contained 980 g of food, including 

 four 25- to 30-cm herring, Clupea harengus, three 

 partly digested (total weight 340 g) and one skele- 

 ton (15 g); and one partly digested short-finned 

 squid, Illex illecebrocus (anterior mantle length 

 17.5 cm, weight 90 g), with remains of 10 other 

 squid of this species (represented by 5 complete 

 pairs of beaks plus 5 single anterior beaks). Mean 

 length of anterior beaks (± SD) was 1.42 ± 0.03 

 cm, corresponding to mantle lengths from 17 to 19 

 cm (Testaverde^). Also 10 left and 11 right otoliths 

 from silver hake, Merluccius hilinearis, (mean size 

 ± SD = 1.15 ± 0.06 cm) indicated consumption of 

 at least 11 fish of 22-26 cm fork length (Nichy 

 1969). 



From these data and the literature it appears 

 that C harengus and/, illecebrocus are staples in 

 the summer diet of white-sided dolphins. A 161-kg 

 female collected on 14 September 1954, off Cape 

 Cod contained 12 fresh herring, digested fish (ap- 

 parently herring), and squid (Schevill 1956). A 

 180-cm long male driven ashore with pothead 

 whales, Globicephala melaena, in Newfoundland 

 on 30 July 1954, contained herring and short- 

 finned squid (Sergeant and Fisher 1957). Short- 

 finned squid was the most common food in the 

 stomachs of white-sided dolphins which mass- 

 stranded at Lingley Cove, Maine, on 6 September 

 1974; however, no herring were found despite the 

 fact that "brit" herring were present in the cove 

 (Geraci et al. see footnote 1). Smelt, Osmerus mor- 

 dax, remains, were found in five individuals; silver 

 hake had been eaten by one individual; and un- 

 identified crustacean remains were found in 

 another stomach. 



Schools of white-sided dolphins were unusually 

 common in the Gulf of Maine in 1976, perhaps 

 because squid were abundant, possibly as a result 

 of this year's unusually high sea temperatures 



'Bones were bleached and dried in the laboratory. 



^Testaverde, S.A. 1975. An informal discussion concerning the 

 cestode Phyllobothrium sp. in squid, Illex illecebrocus illece- 

 brocus and its possible relationship to marine mammals. Un- 

 publ. manuscr., 20 p. 



475 



