GRAY WHALE CALF PRODUCTION 1994–2000: ARE OBSERVED FLUCTUATIONS RELATED TO CHANGES IN SEASONAL ICE COVER?

• DOI: 10.1111/j.1748-7692.2002.tb01023.x
• Publication Date: 2006-08-26T20:23:59Z
• Authors: Wayne L. Perryman; Meghan A. Donahue; Peter C. Perkins; Stephen B. Reilly
• Keywords: 0106 biological sciences; 14. Life underwater; 01 natural sciences

A bstract We conducted shore‐based sighting surveys to estimate the number of northbound migrating gray whale calves passing Piedras Blancas, California, for seven consecutive years (1994–2000). In addition, we aerial determine offshore distribution migration in 1994 and 1995, measured day/night rates with thermal sensors 1994–1996, maintained concurrent replicate watches near peak each proportion cow/calf pairs missed by standard watch team. During good weather, counted 325, 194, 407, 501, 440, 141, 96 during 1994–2000, respectively. Correcting these counts periods not on missed, produced final estimates 945 (SE = 68.21) 1994, 619 67.19) 1,146 70.67) 1996, 1,431 82.02) 1997, 1,388 91.84) 1998, 427 41.10) 1999, 279 34.79) 2000. Calf production indices (calf estimate/total population estimate) are 4.2%, 2.7%, 4.8%, 5.8%, 5.5%, 1.7%, 1.1% Fluctuations calf over this time period were positively correlated length that primary feeding habitat was free seasonal ice previous year.