354 
Fishery Bulletin 99(2) 
Table 2 
Number of shark fins and fillets identified to species level with isoelectric focusing of muscle proteins. All of the fillets were from 
commercial cartons labeled as lemonfish ( Mustelus lenticulatus). No ID = not identified because of a weak protein fingerprint. 
Fin or fillet 
M. lenticulatus 
G. galeus 
S. zygaena 
C. brachyurus 
No ID 
Pectoral fin 
127 
69 
0 
7 
0 
Dorsal fin 
81 
46 
25 
3 
3 
Tail fin 
0 
6 
22 
1 
1 
Unidentified 
1 
0 
0 
0 
0 
Fillet 
113 
27 
28 
26 
1 
cies that are prohibited as target species, S. zygaena and 
C. brachyurus (Table 2). None of the protein fingerprints of 
the fin samples matched with the control samples from S. 
mitsukurii, S. acanthias, P. glauca,L. nasus, I. oxyrinchus, 
or C. isabellum. 
Protein fingerprints of fillets from cartons labelled as 
lemon fish (M. lenticulatus ) showed that the fillets were 
from four shark species, two of which are prohibited as tar- 
get species, S. zygaena and C. brachyurus (Table 2), and 
that 41.8% of the fillets were not the species shown on the 
carton labels. 
Discussion 
To identify the suspect shark fillets and fins, it is essen- 
tial to use a test that can distinguish closely related spe- 
cies of sharks. Occasionally closely related pairs of species 
are found with very similar protein fingerprints, e.g. the 
teleosts tarakihi and king tarakihi, in which case addi- 
tional biochemical tests are sought to identify specimens 
(Smith et ah, 1996). The muscle tissue samples from the 
shark control specimens produced different protein finger- 
print patterns in each species (Fig 1.). Samples of body 
muscle and fin muscle from the same specimen produced 
the same IFF pattern. In addition, samples of M. lenticu- 
latus and G. gcileus from the Bay of Plenty in the North 
Island and east coast South Island showed no intraspe- 
cific variation in protein profiles. These observations dem- 
onstrate that muscle protein profiles are an appropriate 
tool for the identification of shark fillets or fins taken in 
the New Zealand coastal fishery. 
It is not possible to quantify the results and state how 
many fish specimens have been sampled in the fins and 
fillets. Each fish may yield two pectoral, two dorsal, one 
caudal, and one anal fin, but fishermen may discard small 
or damaged fins. Likewise with fillets, each fish may yield 
a minimum of two fillets, but four or more fillets may be 
taken from large specimens. Nevertheless the results indi- 
cate that both quota and nonquota species are being land- 
ed for the fillet and fin markets, and that the domestic 
market has cartons of mislabelled species. Around 40% of 
the fillets tested in our study were not the species on the 
label — M. lenticulatus (Table 2). Such observations dem- 
onstrate that shark landings recorded in New Zealand wa- 
ters may be inaccurate, which will not only confound catch 
statistics but may compromise assessments upon which 
regulatory decisions are made. The mislabeled fillets iden- 
tified in our study suggest that effort is targeting non- 
ITQ species or that prohibited target species such as Car- 
charhinus brachyurus (prohibited in area 1), and Sphyima 
zygaena (prohibited in all areas) are being landed. 
Unlike other biochemical techniques, such as allozyme 
and DNA markers, the protein fingerprints revealed by 
IEF show little intraspecific variation (Lundstrom, 1981). 
Most individuals from the same species have identical pro- 
tein fingerprints. When protein fingerprints vary among 
individuals from the same species, the differences are re- 
stricted to the presence or absence of one or a few of the 
protein bands; the majority of bands are shared among all 
individuals. 
Isoelectric focusing is a relatively quick and cheap iden- 
tification technique (Lundstrom, 1981) compared with 
DNA-based extraction methods. One operator is able to 
process and identify up to 100 specimens in one working 
day. The IEF technique works well with fresh and frozen 
material and produces clear protein profiles. However, 
some proteins denature when they are heat-treated (Keen- 
an and Shaklee, 1985). Therefore, shark products, such as 
sun-dried fins, may require alternative methods, such as 
polyacrylamide gel electrophoresis of parvalbumins (Keen- 
an and Shaklee, 1985) or DNA-based methods (Martin, 
1993; Heist and Gold, 1998), for species identification. 
Acknowledgments 
We are grateful to Mark Scott and Brent Lincoln from 
the Ministry of Fisheries, Tauranga, for supplying fishery 
samples and bringing the issue of shark fin identification 
to our attention. We thank three anonymous referees for 
constructive comments on the manuscript. This project 
was supported by the New Zealand Ministry of Fisheries, 
project number MOF802, species identification. 
Literature cited 
Bartlett, S. E., and W. S. Davidson. 
1991. Identification of Thunnus tuna species by the poly- 
