New Zealand Journal of Marine and Freshwater Research abstracts
Trends and population characteristics of striped marlin, Tetrapturus
audax caught in the New Zealand recreational fishery
R. K. Kopf
P. S. Davie
Institute of Veterinary, Animal and Biomedical Sciences
Massey University
Private Bag 11 222
Palmerston North, New Zealand
email: kkopf1@lycos.com
J. C. Holdsworth
Bluewater Marine Research
Clements Road
RD3, Whangarei, New Zealand
Abstract Size trends and population characteristics
of striped marlin, Tetrapturus audax, caught in the New Zealand recreational
fishery were evaluated using club records from the Bay of Islands Swordfish
Club (BOISC) from 1925 to 2003 (n = 15 114) and biological samples
from northern New Zealand collected from 1985 to 1994 (n = 684). Average
weight (kg) ± SE of striped marlin declined 6Ð9 kg every 20 years
between 1925 (124.2 ± 1.0 kg) and 2003 (100.1 kg ± 0.4). Weight
(H14843 = 444.58, P < 0.001) and condition (H443
= 37.54, P < 0.001) increased significantly throughout the recreational
fishing season (DecemberÐMay). No differences were observed in the lower
jaw-fork length (LJFL)-weight (W) relationship between sexes or years but
average weight of females (106.2 ± 1.1 kg) was significantly greater
than males (90.2 ± 1.2 kg) from 1985 to 1994 (F684
= 88.37, P < 0.001). Negative allometric growth (W = 2E -08 LJFL2.88)
was recorded for all striped marlin. Individual growth was modelled by fitting
backcalculated LJFL to eight age classes derived from dorsal spine measurements
(n = 94) using the von Bertalanffy growth equation (r2
= 0.96). The parameters estimated in the von Bertalanffy growth equation were
asymptotic length (L°) = 3010 mm, annual growth rate (K) =
0.22, age (yr) at hypothetical length 0 (t0) = Ð0.04.
Keywords billfish; size structure; length-weight relationship;
growth; exploitation; stock assessment
M04150; Online publication date 30 August 2005 Received 8 November 2004;
accepted 25 May 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
1145–1156
0028–8330/05/3905–1145 © The Royal Society of New Zealand 2005
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