Time filter

Source Type

Box Elder, HI, United States

Aschettino J.M.,Hawaii Pacific University | Aschettino J.M.,Cascadia Research Collective | Baird R.W.,Cascadia Research Collective | Mcsweeney D.J.,Wild Whale Research Foundation | And 6 more authors.
Marine Mammal Science | Year: 2012

Abstract: Despite the presence of melon-headed whales in tropical and subtropical waters worldwide, little is known about this species. To assess population structure in Hawai'i, dedicated field efforts were undertaken from 2000 to 2009. Using only good quality photographs, there were 1,433 unique photo-identified individuals, of which 1,046 were distinctive. Of these, 31.5% were seen more than once. Resighting data combined with social network analyses showed evidence of two populations-a smaller, resident population, seen exclusively off the northwest region of the island of Hawai'i, and a larger population, seen throughout all the main Hawaiian Islands (hereafter the "main Hawaiian Islands" population). A Bayesian analysis examining the probability of movements of individuals between populations provided a posterior median dispersal rate of 0.0009/yr (95% CI = 0-0.0041), indicating the populations are likely demographically independent. Depth of encounters with the Hawai'i Island resident population was significantly shallower (median = 381 m) than those with the main Hawaiian Islands population (median = 1,662 m). Resightings of individuals have occurred up to 22 yr apart for the Hawai'i Island resident population and up to 13 yr apart for the main Hawaiian Islands population, suggesting long-term residency to the islands for both populations. Published 2011. This article is a US Government work and is in the public domain in the USA.

Martien K.K.,Southwest Fisheries Science Center | Baird R.W.,Cascadia Research Collective | Hedrick N.M.,Southwest Fisheries Science Center | Gorgone A.M.,National Oceanic and Atmospheric Administration | And 4 more authors.
Marine Mammal Science | Year: 2012

We used mitochondrial and nuclear genetic markers to investigate population structure of common bottlenose dolphins, Tursiops truncatus, around the main Hawaiian Islands. Though broadly distributed throughout the world's oceans, bottlenose dolphins are known to form small populations in coastal waters. Recent photo-identification data suggest the same is true in Hawaiian waters. We found genetic differentiation among (mtDNA ΦST= 0.014-0.141, microsatellite F'ST= 0.019-0.050) and low dispersal rates between (0.17-5.77 dispersers per generation) the main Hawaiian Island groups. Our results are consistent with movement rates estimated from photo-identification data and suggest that each island group supports a demographically independent population. Inclusion in our analyses of samples collected near Palmyra Atoll provided evidence that the Hawaiian Islands are also occasionally visited by members of a genetically distinct, pelagic population. Two of our samples exhibited evidence of partial ancestry from Indo-Pacific bottlenose dolphins (T. aduncus), a species not known to inhabit the Hawaiian Archipelago. Our findings have important implications for the management of Hawaiian bottlenose dolphins and raise concerns about the vulnerability to human impacts of pelagic species in island ecosystems. © 2011 by the Society for Marine Mammalogy Published 2011. This article is a US Government work and is in the public domain in the USA.

Mahaffy S.D.,Cascadia Research Collective | Mahaffy S.D.,Portland State University | Baird R.W.,Cascadia Research Collective | Mcsweeney D.J.,Wild Whale Research Foundation | And 2 more authors.
Marine Mammal Science | Year: 2015

Studies of short-finned pilot whales suggest they travel in stable mixed-sex groups composed of strongly associated individuals; however, temporal analyses of social structure are lacking. To examine site fidelity, association patterns, and temporal relationships, we analyzed data from 267 encounters of this species off the island of Hawai'i from 2003 through 2007, identifying 448 distinctive individuals (68.1% seen more than once). About 72% of the whales were linked by association into a single social network, suggesting the possibility of multiple populations using the area. Sighting histories suggested that only some individuals exhibit high site fidelity. Individuals demonstrated preferential associations and community division was strongly supported by average-linkage hierarchical cluster analysis of the association data. Nine longitudinally stable social units composed of key individuals and their constant companions were identified. Qualitative assignment of age and sex classes of unit members indicated that some segregation between adult males and female/calf pairs may occur. Temporal analyses of individuals encountered on the same day indicate stable long-term associations. Differential patterns of residency and site fidelity were unexpected and may be indicative of multiple populations around the main Hawaiian Islands. The presence of a resident population demonstrating strong, long-term site fidelity and associations off Hawai'i Island may warrant special management considerations. © 2015 Society for Marine Mammalogy.

Baird R.W.,Cascadia Research Collective | Mahaffy S.D.,Cascadia Research Collective | Gorgone A.M.,Cascadia Research Collective | Cullins T.,Wild Dolphin Foundation | And 5 more authors.
Marine Mammal Science | Year: 2015

We assessed scarring patterns as evidence of fisheries interactions for three populations of false killer whales in Hawai'i. Bycatch of the pelagic population in the tuna longline fishery exceeds their Potential Biological Removal level. Scarring was assessed by seven evaluators as consistent, possibly consistent, or not consistent with fisheries interactions, and average scores computed. Scores were highest for scarred main Hawaiian Island (MHI) false killer whales, followed by pelagic and Northwestern Hawaiian Island (NWHI) individuals. Considering only whales for which the majority of evaluators scored scarring as consistent revealed significant differences among populations in the percentage of individuals scarred; MHI: 7.5%, pelagic: 0%, NWHI: 0%. Assessment by social cluster for the MHI population showed that 4.2% of Cluster 1, 7.1% of Cluster 2, and 12.8% of Cluster 3 individuals had such scarring, although differences between clusters were not statistically significant. There was a significant sex bias; all sexed individuals (n = 7) with injuries consistent with fisheries interactions were female. The higher proportion of MHI individuals with fisheries-related scarring suggests that fisheries interactions are occurring at a higher rate in this population. The bias towards females suggests that fisheries-related mortality has a disproportionate impact on population dynamics. Copyright © 2015 Society for Marine Mammalogy.

Baird R.W.,Cascadia Research Collective | Schorr G.S.,Cascadia Research Collective | Webster D.L.,Cascadia Research Collective | McSweeney D.J.,Wild Whale Research Foundation | And 3 more authors.
Endangered Species Research | Year: 2010

There are 2 recognized stocks of false killer whales Pseudorca crassidens in the US Exclusive Economic Zone surrounding Hawai'i, a small demographically isolated population around the main Hawaiian Islands and a larger offshore ('pelagic') population. Recent evidence suggests the insular population may have declined precipitously over the last 20 yr, and one possible contributing factor is interactions with offshore longline fisheries or other hook and line fisheries. To assess movements and habitat use, satellite tags were remotely deployed on individuals in 3 groups from the insular population and one from the offshore population. Although tagged off the leeward side of the island of Hawai'i, individuals from the insular population regularly moved to the windward sides of the islands. Some insular individuals moved extensively and rapidly among islands, while other individuals remained associated with the island of Hawai'i for extended periods before moving among the other islands. Comparisons of distances between tagged individuals indicated that individuals within groups disassociated and re-associated over periods of days, occasionally moving more than 100 km apart before re-associating. The offshore individual, tagged 123.8 km offshore, approached to within 62 km of land, inshore of the longline fishery exclusion boundary. The 3 insular groups moved a maximum of 83, 87 and 96 km offshore, respectively, indicating that the distance from shore cannot be used as a strict boundary between the populations, and that individuals from the insular population may overlap with the longline fishery. When combined with photo-identification the results suggest that boundaries between these 2 stocks should be revised. © Inter-Research 2010.

Discover hidden collaborations