Corrie Curtice

Modeling the spatial and temporal dynamics of foraging movements of humpback whales (Megaptera novaeangliae) in the Western Antarctic Peninsula

BackgroundA population of humpback whales (Megaptera novaeangliae) spends the austral summer feeding on Antarctic krill (Euphausia superba) along the Western Antarctic Peninsula (WAP). These whales acquire their annual energetic needs during an episodic feeding season in high latitude waters that must sustain long-distance migration and fasting on low-latitude breeding grounds. Antarctic krill are broadly distributed along the continental shelf and nearshore waters during the spring and early summer, and move closer to land during late summer and fall, where they overwinter under the protective and nutritional cover of sea ice. We apply a novel space-time utilization distribution method to test the hypothesis that humpback whale distribution reflects that of krill: spread broadly during summer with increasing proximity to shore and associated embayments during fall.ResultsHumpback whales instrumented with satellite-linked positional telemetry tags (n = 5), show decreased home range size, amount of area used, and increased proximity to shore over the foraging season.ConclusionsThis study applies a new method to model the movements of humpback whales in the WAP region throughout the feeding season, and presents a baseline for future observations of the seasonal changes in the movement patterns and foraging behavior of humpback whales (one of several krill-predators affected by climate-driven changes) in the WAP marine ecosystem. As the WAP continues to warm, it is prudent to understand the ecological relationships between sea-ice dependent krill and krill predators, as well as the interactions among recovering populations of krill predators that may be forced into competition for a shared food resource.

4. Biologically Important Areas for Selected Cetaceans Within U.S. Waters – West Coast Region

In this review, we combine existing published and unpublished information along with expert judgment to identify and support the delineation of 28 Biologically Important Areas (BIAs) in U.S. waters along the West Coast for blue whales, gray whales, humpback whales, and harbor porpoises. BIAs for blue whales and humpback whales are based on high concentration areas of feeding animals observed from small boat surveys, ship surveys, and opportunistic sources. These BIAs compare favorably to broader habitat-based density models. BIAs for gray whales are based on their migratory corridor as they transit between primary feeding areas located in northern latitudes and breeding areas off Mexico. Additional gray whale BIAs are defined for the primary feeding areas of a smaller resident population. Two small and resident population BIAs defined for harbor porpoises located off California encompass the populations’ primary areas of use. The size of the individual BIAs ranged from approximately 171 to 138,000 km. The BIAs for feeding blue, gray, and humpback whales represent relatively small portions of the overall West Coast area (< 5%) but encompass a large majority (77 to 89%) of the thousands of sightings documented and evaluated for each species. We also evaluate and discuss potential feeding BIAs for fin whales, but none are delineated due to limited or conflicting information. The intent of identifying BIAs is to synthesize existing biological information in a transparent format that is easily accessible to scientists, managers, policymakers, and the public for use during the planning and design phase of anthropogenic activities for which U.S. statutes require the characterization and minimization of impacts on marine mammals. To maintain their utility, West Coast region BIAs should be re-evaluated and revised, if necessary, as new information becomes available.

Why Ecosystem-Based Management May Fail without Changes to Tool Development and Financing

Resource managers rely on tools to enact ecosystem-based management (EBM) principles and frequently express frustration at the difficulty of use and unreliability of available tools. EBM tool developers lack the consistent, long-term funding needed to develop high-quality tools. Through interviews, we determined several reasons for this funding problem including: (a) most EBM tools are developed by academics rather than software professionals and (b) most tools are offered at no cost. These factors create a double-edged sword for managers who cannot afford high license fees or to waste time with low-quality, unmaintained products. Without a fundamental shift in tool funding and development, many potentially useful tools will remain poorly implemented and underused. Without a significant increase in the number of high-quality EBM tools, governmental mandates to implement EBM will remain unfulfilled. This problem can be addressed if both developers and funders change the ways in which they seek and grant financial support.

Multiple-stage decisions in a marine central-place forager

Air-breathing marine animals face a complex set of physical challenges associated with diving that affect the decisions of how to optimize feeding. Baleen whales (Mysticeti) have evolved bulk-filter feeding mechanisms to efficiently feed on dense prey patches. Baleen whales are central place foragers where oxygen at the surface represents the central place and depth acts as the distance to prey. Although hypothesized that baleen whales will target the densest prey patches anywhere in the water column, how depth and density interact to influence foraging behaviour is poorly understood. We used multi-sensor archival tags and active acoustics to quantify Antarctic humpback whale foraging behaviour relative to prey. Our analyses reveal multi-stage foraging decisions driven by both krill depth and density. During daylight hours when whales did not feed, krill were found in deep high-density patches. As krill migrated vertically into larger and less dense patches near the surface, whales began to forage. During foraging bouts, we found that feeding rates (number of feeding lunges per hour) were greatest when prey was shallowest, and feeding rates decreased with increasing dive depth. This strategy is consistent with previous models of how air-breathing diving animals optimize foraging efficiency. Thus, humpback whales forage mainly when prey is more broadly distributed and shallower, presumably to minimize diving and searching costs and to increase feeding rates overall and thus foraging efficiency. Using direct measurements of feeding behaviour from animal-borne tags and prey availability from echosounders, our study demonstrates a multi-stage foraging process in a central place forager that we suggest acts to optimize overall efficiency by maximizing net energy gain over time. These data reveal a previously unrecognized level of complexity in predator–prey interactions and underscores the need to simultaneously measure prey distribution in marine central place forager studies.

1. Biologically Important Areas for Cetaceans Within U.S. Waters - Overview and Rationale

We outline the rationale and process used by the Cetacean Density and Distribution Mapping (CetMap) Working Group to identify Biologically Important Areas (BIAs) for 24 cetacean species, stocks, or populations in seven regions within U.S. waters. BIAs are reproductive areas, feeding areas, migratory corridors, and areas in which small and resident populations are concentrated. BIAs are region-, species-, and time-specific. Information provided for each BIA includes the following: (1) a written narrative describing the information, assumptions, and logic used to delineate the BIA; (2) a map of the BIA; (3) a list of references used in the assessment; and (4) a metadata table that concisely details the type and quantity of information used to define a BIA, providing transparency in how BIAs were designated in a quick reference table format. BIAs were identified through an expert elicitation process. The delineation of BIAs does not have direct or immediate regulatory consequences. Rather, the BIA assessment is intended to provide the best available science to help inform regulatory and management decisions under existing authorities about some, though not all, important cetacean areas in order to minimize the impacts of anthropogenic activities on cetaceans and to achieve conservation and protection goals. In addition, the BIAs and associated information may be used to identify information gaps and prioritize future research and modeling efforts to better understand cetaceans, their habitat, and ecosystems.

5. Biologically Important Areas for Cetaceans Within U.S. Waters – Hawai‘i Region

Of the 18 species of odontocetes known to be present in Hawaiian waters, small resident populations of 11 species—dwarf sperm whales, Blainville’s beaked whales, Cuvier’s beaked whales, pygmy killer whales, short-finned pilot whales, melonheaded whales, false killer whales, pantropical spotted dolphins, spinner dolphins, rough-toothed dolphins, and common bottlenose dolphins—have been identified, based on two or more lines of evidence, including results from small-boat sightings and survey effort, photo-identification, genetic analyses, and satellite tagging. In this review, we merge existing published and unpublished information along with expert judgment for the Hawai‘i region of the U.S. Exclusive Economic Zone and territorial waters in order to identify and support the delineation of 20 Biologically Important Areas (BIAs) for these small and resident populations, and one reproductive area for humpback whales. The geographic extent of the BIAs in Hawaiian waters ranged from approximately 700 to 23,500 km. BIA designation enhances existing information already available to scientists, managers, policymakers, and the public. They are intended to provide synthesized information in a transparent format that can be readily used toward analyses and planning under U.S. statutes that require the characterization and minimization of impacts of anthropogenic activities on marine mammals. Odontocete BIAs in Hawai‘i are biased toward the main Hawaiian Islands and populations off the island of Hawai‘i, reflecting a much greater level of research effort and thus certainty regarding the existence and range of small resident populations off that island. Emerging evidence of similar small resident populations off other island areas in Hawaiian waters suggest that further BIA designations may be necessary as more detailed information becomes available.

3. Biologically Important Areas for Cetaceans Within U.S. Waters – Gulf of Mexico Region

In this review, we merge existing published and unpublished information along with expert judgment to identify and support the delineation of 12 Biologically Important Areas (BIAs) in U.S. waters of the Gulf of Mexico for Bryde’s whales and bottlenose dolphins. BIAs are delineated for small and resident populations to enhance existing information already available to scientists, managers, policymakers, and the public. BIAs ranged in size from approximately 117 to over 23,000 km. BIAs are intended to provide synthesized information in a transparent format that can be readily used toward the analyses and planning under U.S. statutes that require the characterization and minimization of impacts of anthropogenic activities on marine mammals. BIAs are not intended to represent all important areas for consideration in planning processes; in particular, areas of high marine mammal density, typically identified based on a combination of systematic visual and/or acoustic detections coupled with quantitative modeling, are very important to consider, where available, in any assessment. To maintain their utility, Gulf of Mexico BIAs should be re-evaluated and revised, if necessary, as new information becomes available.

6. Biologically Important Areas for Cetaceans Within U.S. Waters – Gulf of Alaska Region

We integrated existing published and unpublished information to delineate Biologically Important Areas (BIAs) for fin, gray, North Pacific right, and humpback whales, and belugas in U.S. waters of the Gulf of Alaska. BIAs are delineated for feeding, migratory corridors, and small and resident populations. Supporting evidence for these BIAs came from aerial-, land-, and vessel-based surveys; satellitetagging data; passive acoustic monitoring; traditional ecological knowledge; photoand genetic-identification data; whaling data, including catch and sighting locations and stomach contents; prey studies; and anecdotal information from fishermen. The geographic extent of the BIAs in this region ranged from approximately 900 to 177,000 km. Information gaps identified during this assessment include (1) reproductive areas for fin, gray, and North Pacific right whales; (2) detailed information on the migration routes of all species; (3) detailed information on the migratory timing of all species except humpback whales; and (4) cetacean distribution, density, and behavior in U.S. Gulf of Alaska waters off the continental shelf. To maintain their utility, these BIAs should be re-evaluated and revised, if necessary, as new information becomes available.