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    In:  http://aquaticcommons.org/id/eprint/9678 | 403 | 2012-08-14 16:33:44 | 9678 | United States National Marine Fisheries Service
    Publikationsdatum: 2021-07-08
    Beschreibung: The 19th century commercial ship-based fishery for gray whales, Eschrichtius robustus, in the eastern North Pacific began in 1846 and continued until the mid 1870’s in southern areas and the 1880’s in the north. Henderson identified three periods in the southern part of the fishery: Initial, 1846–1854; Bonanza, 1855–1865; and Declining, 1866–1874. The largest catches were made by “lagoon whaling” in or immediately outside the whale population’s main wintering areas in Mexico—Magdalena Bay, Scammon’s Lagoon, and San Ignacio Lagoon. Large catches were also made by “coastal” or “alongshore” whaling where the whalers attacked animals as they migrated alongthe coast. Gray whales were also hunted to a limited extent on their feeding grounds in the Bering and Chukchi Seas in summer.Using all available sources, we identified 657 visits by whaling vessels to the Mexican whaling grounds during the gray whale breeding and calving seasons between 1846 and 1874. We then estimated the total number of such visits in which the whalers engaged in gray whaling. We also read logbooks from a sample of known visits to estimate catch per visit and the rate at which struck animals were lost. This resulted in an overall estimate of 5,269 gray whales(SE = 223.4) landed by the ship-based fleet (including both American and foreign vessels) in the Mexican whaling grounds from 1846 to 1874. Our “best” estimate of thenumber of gray whales removed from the eastern North Pacific (i.e. catch plus hunting loss) lies somewhere between 6,124 and 8,021, depending on assumptions about survival of struck-but-lost whales. Our estimates can be compared to those by Henderson (1984), who estimated that5,542–5,507 gray whales were secured and processed by ship-based whalers between 1846 and 1874; Scammon (1874), whobelieved the total kill over the same period (of eastern gray whales by all whalers in all areas) did not exceed 10,800; and Best (1987), who estimated the total landedcatch of gray whales (eastern and western) by American ship-based whalers at 2,665 or 3,013 (method-dependent) from 1850 to 1879.Our new estimates are not high enough to resolve apparent inconsistencies between the catch history and estimates ofhistorical abundance based on genetic variability. We suggest several lines of further research that may help resolve these inconsistencies.
    Schlagwort(e): Conservation ; Fisheries ; Management
    Repository-Name: AquaDocs
    Materialart: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 26-65
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2020-01-23
    Beschreibung: Density surface models (DSMs) are an important tool in the conservation and management of cetaceans. Most previous applications of DSMs have adopted a two-step approach to model fitting (hereafter referred to as the Two-Stage Method), whereby detection probabilities are first estimated using distance sampling detection functions and subsequently used as an offset when fitting a density-habitat model. Although variance propagation techniques have recently become available for the Two-Stage Method, most previous applications have not propagated detection probability uncertainty into final density estimates. In this paper, we describe an alternative approach for fitting DSMs based on Bayesian hierarchical inference (hereafter referred to as the Bayesian Method), which is a natural framework for simultaneously propagating multiple sources of uncertainty into final estimates. Our framework includes (1) a mark-recapture distance sampling observation model that can accommodate two team line transect data, (2) an informed prior for the probability a group of animals is at the surface and available for detection (i.e. surface availability) (3) a density-habitat model incorporating spatial smoothers and (4) a flexible compound Poisson-gamma model for count data that incorporates overdispersion and zero-inflation. We evaluate our method and compare its performance to the Two-Stage Method with simulations and an application to line transect data of fin whales (Balaenoptera physalus) off the east coast of the USA. Simulations showed that both methods had low bias (
    Digitale ISSN: 2167-8359
    Thema: Biologie , Medizin
    Publiziert von PeerJ
    Standort Signatur Erwartet Verfügbarkeit
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