Smith and Benson: Biochemical identification of shark fins and fillets 
353 
Isoelectric focusing 
Small samples (about 0.5 g) of white muscle were removed 
from each of the tissue samples taken from the fins and 
fillets and from control samples taken from known speci- 
mens of New Zealand shark species. The muscle samples 
were homogenized individually in two volumes of cold 
(4°C) deionised water and centrifuged at 12,000 g for 
five minutes at 4°C. The clear supernatants were placed 
on filter paper wicks that were placed directly onto aga- 
rose IEF gels (Amersham Pharmacia Biotech, Uppsala) 
on a flat bed IEF system (Amersham Pharmacia Biotech, 
Uppsala). The 1-mm 1 7c agarose gels were made up in wide 
range pharmalyte, pH 3-10 (Amersham Pharmacia Bio- 
tech, Uppsala), and focused at 1500 volts for 90 minutes. 
After focusing, the proteins were fixed, washed, stained 
with coomassie brilliant blue (BDH Laboratory Supplies, 
Poole), destained, and dried (Benson and Smith, 1989). An 
initial gel was run with control samples only to ensure 
that each species produced a unique protein fingerprint. 
In addition, samples of body muscle from the head, mid, 
and tail regions were compared with samples of muscle 
from the base of pectoral and dorsal fins taken from the 
same specimens of M. lenticulatus and S. zygaena . Twenty- 
five suspect and seven control samples were run on subse- 
quent gels. The same control samples were used in each 
IEF gel to avoid mismatches between gels. 
Results 
The muscle tissue samples from the control specimens 
produced different protein fingerprint patterns in each 
species (Fig. 1). Tests of samples of body muscle and fin 
muscle from the same specimen produced the same IEF 
pattern, demonstrating that the muscle control samples 
were suitable for identification of fillet or fin samples. 
Samples of M. lenticulatus and G. galeus from the Bay of 
Plenty and east coast South Island showed no intraspe- 
cific variation in protein profiles. 
The fins could be grouped into three types based on 
shape: dorsal, pectoral, and caudal (or tail). There was a 
wide range of sizes from 7 to 28 cm. It is possible that some 
small dorsal fins may have been anal fins or second dorsal 
fins. Most fins were of a pale gray color, but some were a 
darker gray color and had a narrow black margin; most of 
these latter fins had a narrower shape than the pale gray 
dorsal fins. A few pectoral fins were dark gray on one sur- 
face and light gray on the other surface. None of the fins 
had a spine or showed sign of a spine having been cut out. 
The protein fingerprints of most of the suspect shark 
fins matched with one of the fingerprint patterns of M. len- 
ticulatus, G. galeus, S. zygaena, or C. brachyurus (Table 2). 
Four of the 392 fins produced a weak and indistinct finger- 
print pattern that could not be matched to any of the con- 
trol samples. Around 10 r /( of the fins were from two spe- 
