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Cahoon M.K.,Joint Institute for Marine and Atmospheric Research | Littnan C.L.,National Oceanic and Atmospheric Administration | Longenecker K.,Bishop Museum | Carpenter J.R.,University of Hawaii at Manoa
Endangered Species Research | Year: 2013

Divergent trends in population abundance of Endangered Hawaiian monk seals Monachus schauinslandi are apparent between the northwestern Hawaiian Islands (NWHI) and the main Hawaiian Islands (MHI). The smaller, recently established MHI seal population is increasing, exhibits higher juvenile survival, and seals appear to be in better condition overall relative to seals in the NWHI. Using traditional dietary analysis we characterize the diet of MHI monk seals for the first time and examine the hypothesis that diet and prey availability may be driving these regional trends. Prey remains from feces and regurgitates (n = 120) were identified to the lowest possible taxonomic level and compared with results from NWHI historical data. The most common prey taxa, by percent frequency of occurrence, were Balistidae (48.3%), Crusta cea (37.5%), Acanthuridae (32.5%), Muraenidae (30.8%), Serranidae (20.8%), Cephalopoda (18.3%), Holocentridae (17.5%), Labridae (16.7%), and Scaridae (10.8%). Results indicate that MHI and NWHI seals eat similar diets; however, an incongruity in body conditions of seals between regions indicates a possible difference in intra- or inter-specific competition, prey availability, and quality. Further research assessing foraging behavior and habitat use would aid in identifying the regional differences observed. © Inter-Research 2013. Source

Brown E.,Kalaupapa National Historical Park | Hughes G.,Kalaupapa National Historical Park | Watanuki R.,Kalaupapa National Historical Park | Johanos C.T.,National Oceanic and Atmospheric Administration | Wurth T.,Joint Institute for Marine and Atmospheric Research
Aquatic Mammals | Year: 2011

The Hawaiian monk seal (Monachus schauin-slandi) is one of the most endangered marine mammals on earth, with the majority (90%) of the population found in the relatively uninhabited Northwestern Hawaiian Islands (NWHI) and the remaining 10% in the heavily developed main Hawaiian Islands (MHI). Since 1998, the total population has declined 4%/y to ~1,100 animals. Despite this trend, the population in the MHI is increasing, with monk seals pupping at Kalaupapa National Historical Park on the island of Moloka'i. Long-time human residents in Kalaupapa indi-cated that monk seals rarely used the beaches prior to 1997, and no births had been observed since at least 1941. Since 1997, a total of 53 pups have been born, with births increasing at an aver-age annual rate of 26.6%. Reproductively active females born at Kalaupapa exhibited a 55.6% site fidelity. Spatially, monk seal density was higher on sandy beaches (2.0 monk seals km -1) than basalt (0.3 monk seals km -1) habitat. Temporally, monk seal density was highest during the late spring and early summer due to the presence of mother-pup pairs. After weaning, monk seals also used adja-cent basalt habitat and typically moved away from Kalaupapa at the onset of winter; since 2009, monk seal sightings have increased throughout the year. Explanations for the emergence of the pupping area include suitable habitat characteristics (e.g., protected shallow water habitat, high prey abun-dance, and low predator/competitor abundance), reduction of human activities (e.g., elimination of cattle in 1985, sparse [3.4 people km -2] and declin-ing [90% since 1900] human population, and low public visitation [8,494 people y -1]), and a sup-portive community. Current management actions include habitat-use surveys, population studies, community presentations, and law enforcement patrols. Kalaupapa has become a productive pupping area for monk seals in the MHI, and the establishment of a birthing area provides hope for the survival of this endangered species. Source

Nadon M.O.,University of Miami | Nadon M.O.,Joint Institute for Marine and Atmospheric Research | Nadon M.O.,National Oceanic and Atmospheric Administration | Ault J.S.,University of Miami | And 3 more authors.
PLoS ONE | Year: 2015

The coral reef fish community of Hawaii is composed of hundreds of species, supports a multimillion dollar fishing and tourism industry, and is of great cultural importance to the local population. However, a major stock assessment of Hawaiian coral reef fish populations has not yet been conducted. Here we used the robust indicator variable "average length in the exploited phase of the population (L¯)", estimated from size composition data from commercial fisheries trip reports and fishery-independent diver surveys, to evaluate exploitation rates for 19 Hawaiian reef fishes. By and large, the average lengths obtained from diver surveys agreed well with those from commercial data. We used the estimated exploitation rates coupled with life history parameters synthesized from the literature to parameterize a numerical population model and generate stock sustainability metrics such as spawning potential ratios (SPR). We found good agreement between predicted average lengths in an unfished population (from our population model) and those observed from diver surveys in the largely unexploited Northwestern Hawaiian Islands. Of 19 exploited reef fish species assessed in the main Hawaiian Islands, 9 had SPRs close to or below the 30% overfishing threshold. In general, longer-lived species such as surgeonfishes, the redlip parrotfish (Scarus rubroviolaceus), and the gray snapper (Aprion virescens) had the lowest SPRs, while short-lived species such as goatfishes and jacks, as well as two invasive species (Lutjanus kasmira and Cephalopholis argus), had SPRs above the 30% threshold. Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Source

Fautin D.,University of Kansas | Dalton P.,University of Washington | Incze L.S.,University of Southern Maine | Leong J.-A.C.,Hawaii Institute of Marine Biology | And 13 more authors.
PLoS ONE | Year: 2010

Marine biodiversity of the United States (U.S.) is extensively documented, but data assembled by the United States National Committee for the Census of Marine Life demonstrate that even the most complete taxonomic inventories are based on records scattered in space and time. The best-known taxa are those of commercial importance. Body size is directly correlated with knowledge of a species, and knowledge also diminishes with distance from shore and depth. Measures of biodiversity other than species diversity, such as ecosystem and genetic diversity, are poorly documented. Threats to marine biodiversity in the U.S. are the same as those for most of the world: overexploitation of living resources; reduced water quality; coastal development; shipping; invasive species; rising temperature and concentrations of carbon dioxide in the surface ocean, and other changes that may be consequences of global change, including shifting currents; increased number and size of hypoxic or anoxic areas; and increased number and duration of harmful algal blooms. More information must be obtained through field and laboratory research and monitoring that involve innovative sampling techniques (such as genetics and acoustics), but data that already exist must be made accessible. And all data must have a temporal component so trends can be identified. As data are compiled, techniques must be developed to make certain that scales are compatible, to combine and reconcile data collected for various purposes with disparate gear, and to automate taxonomic changes. Information on biotic and abiotic elements of the environment must be interactively linked. Impediments to assembling existing data and collecting new data on marine biodiversity include logistical problems as well as shortages in finances and taxonomic expertise. © 2010 Fautin et al. Source

Baker J.D.,National Oceanic and Atmospheric Administration | Johanos T.C.,National Oceanic and Atmospheric Administration | Wurth T.A.,Joint Institute for Marine and Atmospheric Research | Littnan C.L.,National Oceanic and Atmospheric Administration
Marine Mammal Science | Year: 2014

Body length and axillary girth measurements of more than 600 free-ranging Hawaiian monk seals from 1 to 20 yr old were analyzed. Comparison of fitted von Bertalanffy growth models confirmed there is no evidence of sexual dimorphism in this species. Substantial differences in growth patterns were detected among seven subpopulations representing the species entire geographic range. The age at which seals would be expected to attain a reference length of 180 cm ranged from just over 3 yr up to almost 7 yr at the various sites. Subpopulations exhibiting slower growth have previously been found to also exhibit lower age-specific reproductive rates. Differences in growth of seals among sites likely indicate varying environmental conditions determining growth during the time periods represented in the sampled data. © 2014 Society for Marine Mammalogy. Source

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