MEPS 175:13-22 (1998)  -  doi:10.3354/meps175013

ABSTRACT: Identification photographs of individual humpback whales Megaptera novaeangliae were used to investigate movements of whales between Kauai and Hawaii (approximately 500 km apart; the 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 overrepresented in 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 d 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.

KEY WORDS: Humpback whale · Mark-recapture · Photographic identification · Migratory movements