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Fishery Bulletin 99(2) 
Table 1 
Common and scientific names of shark control samples used in the isoelectric focusing analyses. 
Common name 
Other common names 
Scientific name 
Rig 
gummy shark, smoothhound, spotted dogfish, spotted smoothhound. 
lemon fish, pioke 
Mustelus lenticulatus 
School shark 
grey shark, tope, flake, makohuarau, tupere 
Galeorhinus galeus 
Spiny dogfish 
southern spiny dogfish, spurdog, spineback, spikey dog 
Squalus acanthias 
Northern spiny dogfish 
grey spiny dogfish, shortspine spurdog, green-eyed dogfish 
Squalus mitsukurii 
Hammerhead shark 
hammerhead 
Sphyrna zygaena 
Bronze whaler 
whaler 
Carcharhinus brachyurus 
Blue shark 
blue pointer, blue whaler 
Prionace glauca 
Porbeagle 
mackerel shark 
Lamna nasus 
Mako 
mackerel shark 
Isurus oxyrinchus 
Carpet shark 
swell shark, cat shark 
Cephaloscyllium isabellum 
tification of fish product (Tenge et al., 1993) and applied to 
shark species (Weaver et al., 1999); it provides a finer sep- 
aration of proteins than conventional starch and cellulose 
acetate electrophoresis, and the muscle proteins exhibit 
little intraspecific variation. In addition, muscle proteins 
are stable, withstanding repeated freezing and thawing, 
and provide a species profile in one gel, unlike allozyme 
methods, where several gels are required in order to iden- 
tify a range of species. However, some closely related spe- 
cies of teleosts share protein profiles (Bartlett and David- 
son, 1991; Smith et al., 1994; Smith et al., 1996) and thus 
IEF is not always amenable for distinguishing closely re- 
lated species. Our study was undertaken to evaluate aga- 
rose IEF (Lundstrom, 1981, 1983) of shark muscle pro- 
teins in order to provide a quick and robust biochemical 
method to identify shark fins and fillets from commercial 
vessels and the market place. 
Materials and methods 
Samples 
Control samples were taken from shark specimens caught 
on research and commercial vessels around New Zealand 
(Table 1). The specimens were frozen whole at sea and 
returned to the laboratory where the identity of the 
species was confirmed through the use of identification 
keys (Paulin et al., 1989). Samples of white muscle were 
removed from up to ten specimens of each species. For 
Mustelus lenticulatus and Galeorhinus galeus, ten speci- 
mens were tested from the Bay of Plenty, North Island, 
and ten specimens from the east coast South Island. 
Muscle tissue samples were stored in separate, labelled 
bags at -70°C. In addition, samples of body muscle from 
the head, mid, and tail regions were compared with sam- 
ples of muscle from the base of the pectoral and dorsal fins 
taken from the same specimens for both M. lenticulatus 
and Sphyrna zygaena. 
Mustelus lenticulatus and G. galeus are in the same fam- 
ily of smoot hhounds (Triakidae) and lack the characteristic 
dorsal spine of the spiny dogfishes. Whole specimens of M. 
lenticulatus are distinguished from G. galeus by the size 
of the second dorsal fin, which is nearly as large as the 
first dorsal fin in M. lenticulatus , but much smaller in G. 
galeus, and by their teeth; there are small teeth or grind- 
ing plates in M. lenticulatus and distinctive large triangu- 
lar teeth in G. galeus (Paulin et al., 1989). Both species are 
widely distributed in temperate coastal waters and total 
recorded landings in New Zealand are around 3200 tons 
for school shark and 1800 tons for M. lenticulatus (Annala 
et al. 1 ). Two species of spiny dogfish (Squalidae) are com- 
mon in New Zealand waters, the shortspine dogfish ( Squa - 
lus mitsukurii ) in northern waters and the spiny dogfish 
( Squalus acanthias) in southern waters. The hammerhead 
shark (Sphyrna zygaena, family Sphyrinidae) was included 
because small specimens are caught in northern waters of 
New Zealand. The species has a characteristic black mar- 
gin to the fins, but we have noted that juvenile, but not 
adult, G. galeus also have a black margin on the dorsal fin. 
Two species of requiem sharks (family Carcharhinidae), 
Carcharhinus brachyurus and Prionace glauca, are also 
common in coastal waters but are prohibited as target spe- 
cies in northern New Zealand. Lamna nasus, Isurus oxy- 
rinchus, and Cephaloscyllium isabellum, which are caught 
in northern New Zealand, were also included as controls 
(Table 1). 
Three-hundred and eighty shark fins were supplied by 
Ministry of Fisheries staff from commercial shark fisher- 
ies in the Bay of Plenty in northern New Zealand. In the 
laboratory, a small piece of muscle tissue was removed 
from each fin and stored at -70°C. The color and shape of 
each fin was noted and the maximum length between the 
flesh area and the fin tip was recorded; fins were stored 
frozen at -20°C. Eight 10-kg cartons of shark fillets, all 
labelled as lemon fish (=M. lenticulatus ), were tested. A 
small piece of muscle tissue was removed from each indi- 
vidual fillet, labelled, and stored at -70°C prior to isoelec- 
tric focusing. 
