356 



Fishery Bulletin 88(2), 1990 



COMMON DOLPHIN 



Legend 



E3 UNSEXEO 

 d MALES 

 EZI FEMALES 



I \\ 1 t^f '< . i/'/'Ji-y^r/. ]1 . , ^LI. , -11 V 1 , , til,--:! , , 1^^ 



*«' \6«' \1«' \%«' \9* ao* %•''' ^1^ ai* ao^ a%* a^'* al* a*'* a*'* 



LENGTH CLASSES (CM) 



Figure 4 



Length distribution of incidentally captured common 

 dolphins measured by observers aboard foreign fishing 

 vessels off the northeastern United States, 1986-88. Size 

 at attainment of sexual maturity is from Perrin and Reil- 

 ly (1984). 



A total of 169 pilot whales measured during 1986-88 

 included 104 females, 40 males, and 25 not determined 

 (72.2% female). These animals ranged in size from 199 

 to 510 cm (Fig. 5). Of the females, 85% (w = 88) mea- 

 sured 366-510 cm (x 429 cm), which is greater than 

 the average length at attainment of sexual maturity 

 (365 cm) as reported for G. melaena in the western 

 North Atlantic by Perrin and Reilly (1984). The size 

 range for the males was 199-470 cm (x 325 cm). No 

 males recorded by observers reached the average 

 length at attainment of sexual maturity (490 cm) re- 

 ported by Perrin and Reilly (1984). 



early spring in the mid-Atlantic, coincident to the DWF 

 Loligo and Atlantic mackerel fisheries. 



Likewise, pilot whales are also distributed along the 

 outershelf of the mid-Atlantic and southern New 

 England waters of the EEZ during midwinter and 

 spring (December-May). Throughout spring and ear- 

 ly summer, pilot whales move northward along the 

 shelf-edge and by summer-late fall their distribution 

 is most widespread throughout the EEZ (CETAP 1982, 

 Payne et al. 1984). Pilot whales were taken when their 

 distribution was most concentrated along the southern 

 New England shelf-edge in spring. 



Discussion 



Distribution of common dolphins and pilot 

 whales relative to timing and location of take 



The location (Figs. 2, 3) and timing of the incidental 

 take (midwinter to late spring) of these two species are 

 directly related to the seasonal distribution of each 

 species. From mid-January to May, the distribution of 

 common dolphins generally extends from Cape Hat- 

 teras northeastward to Georges Bank in mid- to outer- 

 shelf waters (Hain et al. 1981, CETAP 1982, Payne 

 et al. 1984). During mid- to late summer, many com- 

 mon dolphins move northward out of the EEZ onto the 

 Scotian Shelf (Sergeant 1958, Sergeant and Fisher 

 1957) before returning southward to Georges Bank 

 during late fall and winter. Therefore, the distribution 

 of this species is most restricted during midwinter and 



Incidental take by fishery and country 



A large percentage of common dolphins were taken by 

 Italy during Loligo squid fishing operations. This 

 occurred despite reduction of Italian allocation and 

 effort (i.e., days fished) in the Loligo fishery during 

 1985 and 1986. The Netherlands took a large percent- 

 age of pilot whales in the 1984-88 Atlantic mackerel 

 fishery despite fewer days on grounds than GDR 

 vessels. These takes appear to be more related to dif- 

 ferences in fishing strategies (i.e., gear configuration, 

 trawling and haulback speeds) than total effort. Cur- 

 rently there is insufficient information to evaluate the 

 effect of different fishing techniques between countries 

 on the total take or the k/d rates. Increased observer 

 coverage and documentation of fishing activities should 

 be helpful in evaluating and developing recommenda- 

 tions for modifying current fishing practices, resulting 

 in a reduction of incidental marine mammal mortality. 



