2008 Status Review and Extinction Risk Assessment of Cook Inlet Belugas (Delphinapterus leucas) (original) (raw)
Related papers
Marine Fisheries Review
—Aerial surveys of beluga whales, Delphinapterus leucas, have been conducted annually in Cook Inlet, Alaska, from 1993 to 2012. Beluga whales were seen near the coast and within river mouths in all years, with nearly all of the sightings in the northernmost portions of the inlet after 2000. In this paper, we revisit abundance estimates from 1994 to 2012 and present changes in methods and statistical analyses that have occurred since an earlier publication in 2000. Our objectives include a reanalysis of the abundance estimates over the 19-year aerial survey time series (1994–2012), revising the population tra-jectory through 2012, and estimating population trend rates for endangered Cook Inlet beluga whales. Annual surveys documented a decline of nearly 50% between 1994 and 1998 from an estimated 653 (CV = 0.24) whales to 347 (CV = 0.17) whales. With a very limited hunt (5 whales total taken between 1999 and 2012), the anticipated recovery at a rate of at least 2% per year did not materialize. Instead, from 1999 to 2012, the rate of decline has been-1.60% (SE = 0.75%) per year, with a 97% probability that the growth rate is declining (i.e., less than zero) and a 99.9% probability that the growth rate is less than +2% per year.
2017
The National Marine Fisheries Service (NMFS) has conducted aerial surveys to estimate abundance of the beluga population in Cook Inlet, Alaska, each June, July, or both from 1993 to 2012, after which biennial surveys began in 2014. The current document presents survey results and subsequent analyses yielding an abundance estimate and population trend based on data collected during June 2016. Surveys occurred May 31 -June 9, 2016 (49.2 flight hours). All surveys were flown in twin-engine, high-wing aircraft (i.e., an Aero Commander) at a target altitude of 244 m (800 ft) and speed of 185 km/hour (100 knots), consistent with NMFS' surveys of Cook Inlet conducted in previous years. Tracklines were flown 1.4 km from the shoreline, along the entire Cook Inlet coast, including islands. Additionally, sawtooth pattern tracklines were flown across the inlet in 2016. These aerial surveys effectively covered 40% of the total surface area of Cook Inlet and 100% of the coastline. In particular, most of the upper inlet, north of the East and West Foreland where beluga whales are consistently found, was surveyed seven times (out of seven attempts). Paired, independent observers searched on the coastal side of the plane, where most beluga sightings occur, while a single observer searched on the inlet side. A computer operator/data recorder periodically monitored distance from the shoreline (1.4 km) with a clinometer (angle 10°). After finding beluga groups, a series of aerial passes allowed all observers to each make independent counts of every group. In addition, whale groups were video recorded for later analysis and more precise counts in the laboratory. Belugas were not seen in lower Cook Inlet (south of East and West Foreland) nor in the upper inlet south of North Foreland and Moose Point. Much of the survey period occurred during negative low tides, which expose vast expanses of mudflats and typically line up whales within the deeper channels. Beluga groups were found from Beluga River to the Little Susitna River in the Susitna Delta, along offshore tracklines from North Foreland to Point Possession, near Moose Point shoals south of Point Possession, from Burnt Island to the bluffs approaching Point Possession in Chickaloon Bay, and in Turnagain Arm. The annual sums of medians from aerial counts provide an index of relative abundance, not corrected for estimates of whales missed.
UNUSUAL MORTALITY IN THE DEPLETED COOK INLET BELUGA (DELPHINAPTERUS LEUCAS) POPULATION
Northwestern Naturalist, 2005
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SYNTHESIS OF AVAILABLE INFORMATION ON THE COOK INLET STOCK OF BELUGA WHALES
wherein NMFS requested public comment and pertinent information, followed by a workshop for presentation of scientific information and the collection of additional public comments held 8-9 March 1999 in Anchorage, Alaska. The scientific review was focused on the current status of Cook Inlet belugas: distribution, abundance, trends in abundance, and habitat. The effects of the Alaska Native subsistence harvest and the potential effects of other anthropogenic impacts, as well as beluga natural mortality were also examined. Results of the scientific review confirm that this stock of beluga whales is geographically and genetically isolated from all other stocks. It is now evident that their distribution within Cook Inlet is shrinking, and that there are no large, persistent groups of beluga whales in the Gulf of Alaska. Habitat factors are being examined, including physical, ecosystem and anthropogenic factors. Samples from belugas in Cook Inlet had lower contaminant and heavy metal levels (except copper) than did other stocks of belugas in Alaska. The abundance of beluga whales in Cook Inlet has declined by nearly 50% between 1994 and 1998. The latest abundance estimate, from the June 1998 aerial counts, was 347 whales (SE = 101, CV = 0.29). This estimate includes corrections for surface timings (calculated from suction-cup attached VHF transmitters) and sighting rates (calculated from video analysis). An annual take of approximately 72 whales (averaged for the years 1994-96) has been excessive for this small stock. Options for reducing the harvest levels and increasing the efficiency of the hunt are being developed in cooperation with local hunters.
Aerial Surveys of Beluga Whales, Delphinapterus leucas, in Cook Inlet, Alaska, June 2005 to 2012
The National Marine Fisheries Service (NMFS) has conducted aerial surveys of the beluga population in Cook Inlet, Alaska, each June, July, or both from 1993 to 2012, after which biennial surveys began in 2014. The current document presents survey results and subsequent analyses yielding an abundance estimate and population trend based on data collected during June 2014. Surveys occurred 3-12 June 2014 (52 flight hours). All surveys were flown in twinengine, high-wing aircraft (i.e., an Aero Commander) at a target altitude of 244 m (800 ft) and speed of 185 km/hour (100-120 knots), consistent with NMFS' surveys of Cook Inlet conducted in previous years. Tracklines were flown 1.4 km from the shoreline, along the entire Cook Inlet coast, including islands. Additionally, sawtooth pattern tracklines were flown across the inlet. These aerial surveys effectively covered 32% of the total surface area of Cook Inlet and 100% of the coastline. In particular, most of the upper inlet, north of the Forelands where beluga whales are consistently found, was surveyed six times (out of eight attempts). Paired, independent observers searched on the coastal side of the plane, where virtually all beluga sightings occur, while a single observer searched on the inlet side. A computer operator/data recorder periodically monitored distance from the shoreline (1.4 km) with a clinometer (angle 10°). After finding beluga groups, a series of aerial passes allowed all observers to each make four or more independent counts of every group (i.e., typically 16 counts of each group conducted during eight passes). In addition, whale groups were video recorded for later analysis and more precise counts in the laboratory. Belugas were not seen in lower Cook Inlet (south of East and West Foreland) nor in the upper inlet south of North Foreland and Moose Point. Much of the survey period occurred during low tides that were 5 to 7 ft versus negative low tides, which expose vast expanses of mudflats and typically line up whales within the deeper channels. Because of this, whale groups tended to be more dispersed over the unexposed mudflats in the Susitna delta and Chickaloon Bay. Beluga groups were found from Chuitna River to the Little Susitna River in the Susitna delta, scattered from the Susitna delta to Point Possession, and from Chickaloon River to the bluffs approaching Point Possession. The annual sums of medians from aerial counts provide an index of relative abundance, not corrected for estimates of whales missed. Daily overall medians ranged from 231 iii to 352 whales. The annual median index count of 352 whales represents the highest median count to date for this project. Corrected group sizes ranged from 2 to 168 whales (SD = 53). Similar to the past five survey years, whales were not found in Knik Arm. The greatest numbers were found in the Susitna delta (average group size = 71, range: 2-168) compared to Chickaloon Bay (average groups size = 22, range: 2-79). The abundance estimate was based on 3 days of surveys (9-11 June) where coverage of the upper inlet was complete and observer counts with (11 groups) and without (4 groups) video recordings were obtained for every beluga whale group observed. The abundance estimate of 340 (CV = 0.08, 95% CI = [291,398], Nmin = 318) falls within the range of abundance estimates from the last 10 survey years (312-375 whales). The 10-year trend (2004-2014) was-0.4% /year with a SE of 1.3% (i.e., a declining trend: P (< 0.0) = 62%). During the period since management of the hunt began (1999-2014), the trend was-1.3% /year with a SE of 0.7% (i.e., a declining trend: P (< 0.0) = 97%).
Aerial Surveys of Beluga Whales (Delphinapterus leucas) in Cook Inlet, Alaska, June 2014
AFSC PROCESSED REPORT 2015-03, 2015
The National Marine Fisheries Service (NMFS) has conducted aerial surveys of the beluga population in Cook Inlet, Alaska, each June, July, or both from 1993 to 2012, after which biennial surveys began in 2014. The current document presents survey results and subsequent analyses yielding an abundance estimate and population trend based on data collected during June 2014. Surveys occurred 3-12 June 2014 (52 flight hours). All surveys were flown in twinengine, high-wing aircraft (i.e., an Aero Commander) at a target altitude of 244 m (800 ft) and speed of 185 km/hour (100-120 knots), consistent with NMFS' surveys of Cook Inlet conducted in previous years. Tracklines were flown 1.4 km from the shoreline, along the entire Cook Inlet coast, including islands. Additionally, sawtooth pattern tracklines were flown across the inlet. These aerial surveys effectively covered 32% of the total surface area of Cook Inlet and 100% of the coastline. In particular, most of the upper inlet, north of the Forelands where beluga whales are consistently found, was surveyed six times (out of eight attempts). Paired, independent observers searched on the coastal side of the plane, where virtually all beluga sightings occur, while a single observer searched on the inlet side. A computer operator/data recorder periodically monitored distance from the shoreline (1.4 km) with a clinometer (angle 10°). After finding beluga groups, a series of aerial passes allowed all observers to each make four or more independent counts of every group (i.e., typically 16 counts of each group conducted during eight passes). In addition, whale groups were video recorded for later analysis and more precise counts in the laboratory. Belugas were not seen in lower Cook Inlet (south of East and West Foreland) nor in the upper inlet south of North Foreland and Moose Point. Much of the survey period occurred during low tides that were 5 to 7 ft versus negative low tides, which expose vast expanses of mudflats and typically line up whales within the deeper channels. Because of this, whale groups tended to be more dispersed over the unexposed mudflats in the Susitna delta and Chickaloon Bay. Beluga groups were found from Chuitna River to the Little Susitna River in the Susitna delta, scattered from the Susitna delta to Point Possession, and from Chickaloon River to the bluffs approaching Point Possession. The annual sums of medians from aerial counts provide an index of relative abundance, not corrected for estimates of whales missed. Daily overall medians ranged from 231 iii to 352 whales. The annual median index count of 352 whales represents the highest median count to date for this project. Corrected group sizes ranged from 2 to 168 whales (SD = 53). Similar to the past five survey years, whales were not found in Knik Arm. The greatest numbers were found in the Susitna delta (average group size = 71, range: 2 -168) compared to Chickaloon Bay (average groups size = 22, range: 2 -79). The abundance estimate was based on 3 days of surveys (9-11 June) where coverage of the upper inlet was complete and observer counts with (11 groups) and without (4 groups) video recordings were obtained for every beluga whale group observed. The abundance estimate of 340 (CV = 0.08, 95% CI = [291,398], Nmin = 318) falls within the range of abundance estimates from the last 10 survey years (312 -375 whales). The 10-year trend (2004-2014) was -0.4% /year with a SE of 1.3% (i.e., a declining trend: P (< 0.0) = 62%). During the period since management of the hunt began (1999-2014), the trend was -1.3% /year with a SE of 0.7% (i.e., a declining trend: P (< 0.0) = 97%). iv CONTENTS Abstract .
Distribution of Belugas, Delphinapterus leucas, in Cook Inlet, Alaska, During June/July 1993-2000
2000
ABSTRACT—Aerial surve ys of belugas, centration of belugas (151–288 whales by Delphinapterus leucas, in Cook Inlet were aerial count) was in the northern portion flown each year ,during ,June ,and/or July ,of upper ,Cook Inlet in the ,Susitna River from 1993 to 2000. This project was ,de-,Delta and/or in Knik Arm. Another con- signed to delineate distribution and collect,centration (17–49