Population size of humpback whale, Megaptera novaeangliae, in waters off the Pacific coast of Mexico. (original) (raw)
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Towards an estimate of the Southeastern Pacific humpback whale stock
Between 1991 and 1997 a photo-identification study of Southeastern Pacific humpback whales was carried out on the central coast of Ecuador (1°26'S, 80°50'W), South America. During this period, a total of 219 whales were identified and catalogued by the colouration pattern on the ventral side of their flukes. Naturally marked whales were used to estimate the population through the Petersen's mark-recapture method as modified by Bailey. With data from the final two seasons (1996)(1997), the resultant estimate was 1,922 (95% CI = 77-3,767) whales. Pooling data from the first six years resulted in an estimate of 2,683 (95% CI = 397-4,969) whales. Sources of bias relate to violations of the assumptions of closure and equal catchability conditions. The low inter-yearly resighting rate and a high rate of new discoveries in the last season indicate that only a fraction of the population has so far been identified. Despite the broad confidence interval, these data provide an indication of the current number of whales.
Marine Ecology Progress Series, 2003
Humpback whales Megaptera novaeangliae in the North Atlantic Ocean were severely depleted by exploitation. With legal protection since 1955, substantial recovery is likely to have occurred, but information on abundance and rates of increase has been limited. We present an assessment of humpback whale abundance in the North Atlantic Ocean based upon capturerecapture estimates using naturally marked individuals. These data result from a long-term collaborative effort combining large-scale dedicated projects and incidental data collection, leading to extensive geographical coverage. The application of robust statistical techniques produces estimates of greater accuracy and precision than has previously been possible. Abundance estimates ranging from 5930 to 12 580 individuals, with coefficients of variation (CVs) from 0.07 to 0.39, were calculated for the West Indies breeding population using data from 1979 to 1993. The most precise estimate for the West Indies breeding population is 10 752 (CV = 0.068) for 1992 and 1993. Due to application of new analytical methods, these estimates are larger and more precise than those previously published from similar time periods. The average rate of increase for the West Indies breeding population over a 14 yr period was estimated to be 0.031 (SE = 0.005). The best available estimate for the entire North Atlantic population of humpback whales is 11 570 (95% CI 10 290 to 13 390) based upon samples from 1992 and 1993. However, this estimate may be biased downwards to an unknown extent due to heterogeneity in capture probabilities that do not influence the West Indies estimates.
J. Cetacean Res. Manage, 2002
In recent years, humpback whales (Megaptera novaeangliae) have been observed in the waters of the US mid-Atlantic states (USMA; New Jersey to North Carolina), notably in winter. The level of the mortality in this area (52 recorded deaths from 1990-2000), makes it important to understand the nature and population identity of this aggregation. Of the approximately 100 humpback whales documented in this study, photographs of 41 (live or dead) were of sufficient quality to be compared to catalogues from the Gulf of Maine (GOM, the closest feeding ground) and elsewhere in the North Atlantic. Of 22 live whales, 10 (45.5%) matched to the GOM, 5 (22.7%) to Newfoundland and 1 (4.5%) to the Gulf of St Lawrence (GSL). Of 19 dead whales, 6 (31.6%) were known GOM whales. Although the population composition of the USMA is dominated by GOM whales, lack of recent photographic effort in Newfoundland makes it likely that the observed match rates under represent the true presence of Canadian whales in the region. Length data from 48 stranded whales (18 females, 22 males and 8 of unknown sex) suggest that 39 (81.2%) were first-year animals, 7 (14.6%) were immature and 2 (4.2%) were adults. However, sighting histories of five of the dead whales indicate that some were small for their age and histories of live whales further indicate that the population contains a greater percentage of mature animals than is suggested by the stranded sample. The authors suggest that the study area primarily represents a supplemental winter feeding ground that is used by humpbacks for more than one purpose. From a management perspective, although the only successful matches of mortalities to date have been to the GOM, the observed mixing of live whales from different summer stocks might suggest that the high numbers of mortalities occurring there may not be impacting this single stock alone. Although further data are required before conclusions can be drawn, the mortality rate may be significant for the GOM population and this warrants further investigation.
Population identity of humpback whales (
Journal of Cetacean Research and Management
In recent years, humpback whales (Megaptera novaeangliae) have been observed in the waters of the US mid-Atlantic states (USMA; New Jersey to North Carolina), notably in winter. The level of the mortality in this area (52 recorded deaths from 1990-2000), makes it important to understand the nature and population identity of this aggregation. Of the approximately 100 humpback whales documented in this study, photographs of 41 (live or dead) were of sufficient quality to be compared to catalogues from the Gulf of Maine (GOM, the closest feeding ground) and elsewhere in the North Atlantic. Of 22 live whales, 10 (45.5%) matched to the GOM, 5 (22.7%) to Newfoundland and 1 (4.5%) to the Gulf of St Lawrence (GSL). Of 19 dead whales, 6 (31.6%) were known GOM whales. Although the population composition of the USMA is dominated by GOM whales, lack of recent photographic effort in Newfoundland makes it likely that the observed match rates under represent the true presence of Canadian whales in...
Latin American Journal of Aquatic Mammals, 2021
population parameters of humpback whales in breeding areas to improve management practices. This study also highlights the potential of opportunistic platforms, such as whale watching tour boats, as viable sources of quality information, particularly in contexts when funding is limited. a result. Between 2004 to 2006, project "SPLASH: Structure of Populations, Levels of Abundance and Status of Humpback Whales" (Calambokidis et al., 2008) assessed several parameters of the North Pacific population of humpback whale. SPLASH results reported a yearly population increase of 6.8% and an estimate of 21,808 whales in the whole North Pacific, a number that surpassed pre-whaling population estimates (Barlow et al., 2011). The findings of Calambokidis et al. (2008) from the SPLASH project suggested that the Mexican Pacific was the second most important breeding region for humpback whales of the North Pacific (after the Hawaiian Archipelago), receiving about 40% of wintering humpback whale annually. Medrano et al. (2007) reported that humpback whale population abundance in Banderas Bay was 15 times greater than in the surrounding waters of the Eastern Tropical Pacific and the entrance to the Gulf of California. Later, Martinez-Aguilar (2011) assessed the population abundance of humpback whale in wintering areas of the North Pacific, particularly in Mexican waters (i.e. Baja California, mainland and Revillagigedo) and reported a higher recovery rate for humpback whales wintering in Mexico compared to those wintering in Hawaii. Humpback whale population increases are directly related to oceanographic conditions such as thermal fronts (impacted by climate change) and to El Niño-Southern Oscillations (ENSO) in high latitude summer feeding areas that either directly or indirectly affect prey and habitat availability and therefore, reproductive success (Salvadeo, et al.
Journal of Cetacean Research and Management
Southeastern Pacific humpback whales (Breeding Stock G) breed along the northwestern coast of South America and farther north up to Costa Rica. Photo-identification surveys conducted aboard whalewatching vessels during the migration/breeding season from June to September between 1991 and 2006 off the coast of Ecuador (2°S, 81°W) have produced a database of 1,511 individual whales. Comparisons of photographs produced 190 between-year re-sightings of 155 individual whales. Closed and open capture-recapture models were used to estimate abundance and survival. The best estimate of abundance in 2006 with the Chapman modified-Petersen was 6,504 (95% CI: 4,270-9,907; CV = 0.21).
Estimated Abundance of Humpback Whales off the West Coast of Central and South America (Group G)
2000
Mark-recapture abundance estimates using two samples from the same habitat may be substantially biased, while small sample sizes lead to several other sources of bias in such abundance estimates. When these biases cannot be minimized or accounted for, use of these estimates will lead to problems in fitting assessment models. We present capture-recapture estimates of abundance for Group G humpback