Movements of humpback whales between Kauai and Hawaii: implications
for population structure and abundance estimation in the Hawaiian
Islands
- Cerchio, S., Gabriele, C.M., Norris, T.F., Herman, L.M.
- (C) 1998 Inter-Research
-
- Abstract: Identification photographs of individual humpback
whales Megaptera novaeangliae were used to investigate movements
of whales between Kauai and Hawaiian Islands, USA) during the
winter and spring months of 1989, 1990 and 1991. A total of 1072
individuals were identified, with 40 individuals being sighted
off both islands. There were 15 documented transits between islands
within seasons; 9 whales traveled northwest (from Hawaii to Kauai),
whereas 6 whales traveled southeast (Kauai to Hawaii). Simulation
data indicated that these transit-direction proportions did not
deviate from random expectations (p=0.76); therefore, there was
no directional trend to movement between the islands. The shortest
observed transit was 8 d, indicating that whales can move throughout
the island chain in short periods. Males were significantly over-represented
in the inter-island recaptures (p<= 0.001), and we suggest
that males actively engaged in courtship behaviors are more wide-ranging.
Whales did not show a significant trend to be captured off the
same island in different years (p = 0.08 for Kauai, p = 0.12 for
Hawaii); however, recaptures were few, power was relatively low,
and 1 test approached significance. The observed number of within-season,
between-island recaptures was significantly less than expected
as determined by random simulations (p = 0.013 for Kauai, p =
0.008 for Hawaii), indicating that, during a season, whales are
more likely to be recaptured off the island of initial capture.
There was also evidence suggesting that sub-groups of whales moved
among the islands in loose aggregations: within seasons, the number
of pairs of individuals captured off both islands within 7 days
of each other was significantly greater than expected in random
simulations (p = 0.038). We conclude that complete random mixing
of whales among the islands is unlikely, and should not be assumed
in the context of mark-recapture abundance estimation. Larger
samples with greater coverage of the Hawaiian Islands and higher
recapture probability will be needed to elucidate movement patterns
of the population.
Abstract: Identification photographs of individual humpback
whales Megaptera novaeangliae were used to investigate movements
of whales between Kauai and Hawaiian Islands, USA) during the
winter and spring months of 1989, 1990 and 1991. A total of
1072 individuals were identified, with 40 individuals being
sighted off both islands. There were 15 documented transits
between islands within seasons; 9 whales traveled northwest
(from Hawaii to Kauai), whereas 6 whales traveled southeast
(Kauai to Hawaii). Simulation data indicated that these transit-direction
proportions did not deviate from random expectations (p=0.76);
therefore, there was no directional trend to movement between
the islands. The shortest observed transit was 8 d, indicating
that whales can move throughout the island chain in short periods.
Males were significantly over-represented in the inter-island
recaptures (p<= 0.001), and we suggest that males actively
engaged in courtship behaviors are more wide-ranging. Whales
did not show a significant trend to be captured off the same
island in different years (p = 0.08 for Kauai, p = 0.12 for
Hawaii); however, recaptures were few, power was relatively
low, and 1 test approached significance. The observed number
of within-season, between-island recaptures was significantly
less than expected as determined by random simulations (p =
0.013 for Kauai, p = 0.008 for Hawaii), indicating that, during
a season, whales are more likely to be recaptured off the island
of initial capture. There was also evidence suggesting that
sub-groups of whales moved among the islands in loose aggregations:
within seasons, the number of pairs of individuals captured
off both islands within 7 days of each other was significantly
greater than expected in random simulations (p = 0.038). We
conclude that complete random mixing of whales among the islands
is unlikely, and should not be assumed in the context of mark-recapture
abundance estimation. Larger samples with greater coverage of
the Hawaiian Islands and higher recapture probability will be
needed to elucidate movement patterns of the population.
-
-
Cerchio, S., Gabriele, C.M., Norris, T.F., Herman, L.M. (1998).
Movements of humpback whales between Kauai and Hawaii: implications
for population structure and abundance estimation in the Hawaiian
Islands. Marine Ecology Progress Series, 175, 13-22.
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