Emerging Issue Summary
SPECIES OF INTEREST -- MARINE MAMMALS AND THEIR PREY

Highlights:

  • For some species of marine mammals and marine mammal prey, there is a need for better information on species abundance, seasonal distribution, seasonal movements, and human-animal interactions to support management decisions. Information on species abundance in the Arctic is often unavailable or out-of-date (>8 years old) and information on seasonal distribution and movements is often not at the spatial scales or in the areas where managers need to make decisions. The spatial scale at which distribution and movements are important will depend on the specific management question.
  • At this time, there is still a need for more systematic monitoring of the subsistence harvest of marine mammals and their prey. There is some harvest monitoring of bowhead and beluga whales, polar bears, ice seals, walrus, and fish. There is also systematic monitoring of polar bear and walrus harvest by the U.S. Fish and Wildlife Service. Nevertheless, monitoring for many species must be enhanced and conducted in a systematic manner that will allow managers to fully understand existing harvest practices and changes in existing harvest practices.
  • To assist management decisions, it may be necessary to focus data collection on species that are listed as endangered or threatened under the ESA, depleted under the MMPA, or are the focus of a subsistence harvest.
  • Incorporation of Traditional Ecological Knowledge (TEK) should be a priority when assessing historical information on animal and fish distribution and will be critical to understanding changes in the subsistence harvest.
  • Modeling is needed to focus and integrate studies, develop hypotheses, and predict likely future states.
Marine Mammals
Pacific walrus haulout on the North Slope. (Wendy Loya, TWS)


Overview and Management Relevance:

The immediate and overwhelming conclusion of the STAP to the set of management questions reviewed is that more baseline information (past and current information on basic population parameters) for both biological and physical environments is urgently needed to understand marine mammal population dynamics and elucidate the effects of development, climate change, subsistence harvest, and other stressors on marine mammal populations. As these studies are designed and data are collected, it is imperative that data be made accessible within and across agencies, as well as to stakeholders through avenues such as a central database (e.g., GINA), key conferences, and peer-reviewed papers. When possible, Alaska Natives should be given the opportunity to participate in research projects in their region.

Many concerns and questions raised by managers require integration across a range of spatial scales, multiple stressors to marine mammals or their prey, multiple trophic levels, and multiple years. This is consistent with a broader interest on the parts of many agencies to shift from single species management to ecosystem management, but the roadmap to accomplishing this shift is not clear. It is clear that the types of studies needed will often be expensive and will take years to complete. Uncertainty in how to proceed should not cause paralysis, but will certainly require a combination of careful elucidation of management needs, research planning, modeling to ascertain how best to focus the studies, substantial funding, and long-term programmatic support.

In addition to these broad concerns, the NSSI Senior Staff Committee provided the STAP with specific questions on marine mammals and their prey. STAP responses to these individual questions follow below.

  1. How do we differentiate and assess the separate and combined effects of climate change and development on various species and their interaction?

    Analysis of cumulative impacts of multiple stressors is a critical need that has not been well addressed. Despite voluminous literature on cumulative effects and frequent application of the National Environmental Policy Act (NEPA) process, there is no existing guidance on how to conduct quantitative analyses of monitoring data to differentiate between various types of disturbances. The following approaches may be useful:

    • Resource selection models that incorporate movement data with habitat data;
    • Population dynamics modeling that incorporates subsistence harvest and predation as well as other stressors, such as incidental take and contaminants;
    • Disturbance coefficients established that incorporate species responses to industrial activity and other human and natural disturbances;
    • Habitat availability models under a range of foreseeable development and habitat changes as a result of climate predictions.

    Given the paucity of data on current abundance, seasonal distribution, movements, population dynamics, and other basic biological information for many species, collection of these types of information should be a priority. It would be useful to identify examples of integrative studies that adequately addressed these issues as a starting point.

    Considerable additional information on the independent effects of natural variation, climate change, and anthropogenic activities on species of interest will be needed before cumulative effects can be assessed. Typically, the effect of stressors on animal health is not incorporated in cumulative impact studies. Understanding individual animal health has implications to both the species’ health and survival, as well as to human health in the subsistence harvest communities.

  2. How might a shift in species distribution from sea to land affect land management?

    An already apparent shift in species distribution from sea to land involves increased use of land by polar bears and ice-dependent pinnipeds, especially those whose existing behavioral repertoire includes hauling out on land (walrus, spotted seals). Additional coastal surveys and tagging should be conducted to understand how walrus are using the coastline, and disease surveillance should be improved to document whether the shift to land results in transmission of novel diseases to the marine mammal populations. This kind of shift in distribution may result in an increase in subsistence harvest for some species; again, information on recent historical and current harvest levels and practices will be necessary to understand if an increase in harvests might strain populations.

    In the case of polar bears, the change in distribution (with more animals on land, especially in summer) is expected to result in increased bear-human interactions that may lead to an increase in take of bears in defense of life and property.

    Human activities onshore should be identified and examined to predict how they could affect land usage by marine species. Management will have to adapt operations to incorporate new areas being used by marine mammals. Changes in the level of protection for key pinniped haulout areas may be necessary.

  3. How may this shift affect predator/prey relations on land and/or marine waters?

    In general, the shift of polar bears from sea to land is not expected to result in negative impacts to terrestrial prey resources such as caribou or muskoxen. However, some prey shifting may occur; for example, severe predation of seabird chicks has been attributed to the presence of polar bears on a coastal island in at least one case. To detect a change in prey selection requires long-term (5-10 years) monitoring of seasonal abundance, diet, distribution, and movement of both predators and prey. Stable isotope analyses can be useful in differentiating animals that rely on marine source prey from those that rely on terrestrial source prey.

    There is potential for depletion of local benthic resources if walrus occupy new coastal haulout sites and compete with other benthic feeders such as gray whales, sea ducks, and demersal fish. The benthos in these areas should be inventoried over multiple years to detect local depletion effects.

  4. Will changes in ocean currents affect species distribution and recruitment (e.g., nearshore currents and larval drift)?

    Changes in physical and biological oceanography will change species distribution and recruitment. Evaluating these changes will require interdisciplinary, integrated studies where currents, plankton, and marine mammal (or their prey) densities and behaviors are being studied simultaneously and analyzed together so that relationships between oceanography and marine mammal (or prey) distribution can be understood. A change in fish distribution could be used to highlight a probable change in distribution or population dynamics of marine mammals that forage on that fish; or alternatively, a change in the distribution of a higher predator could be used to identify an underlying change in prey distribution. Most non-commercially important prey species are not being monitored. Small- and large-scale changes in distribution of a variety of species will be needed to assess these factors. A multi-disciplinary site specific monitoring program was initiated by ConocoPhillips and Shell in the Chukchi Sea in 2008, focusing on the collection of data as described above. A second year of pre-development data is scheduled to continue in 2009 and should continue at some level as long as plans exist for exploration drilling and development. Understanding the interannual and seasonal differences of the physical and biological oceanographic conditions may assist in determining the potential changes in these conditions due to anthropogenic stressors, in combination with other ‘natural’ stressors and/or climate change.

    The MMS-funded “BOWFEST” project and the BP and ConocoPhillips Arctic cisco monitoring programs attempt to relate marine mammal and fish distribution to oceanographic conditions, and were identified as good examples of the types of integrative studies needed. Both studies should be continued.

  5. Can prey species shifts in distribution and abundance be better modeled, how and with what precision?

    We are unaware of any modeling being done to estimate future shifts in distribution of prey species, so it was not clear how to “better model” shifts in distribution. There is likely to be insufficient data for modeling shifts in prey at this point, but models would still be important for developing and testing hypotheses about how a system works, so the development of models should not be postponed indefinitely. Substantial new information on prey species in the Arctic will have to be collected, as very little is known about the distribution of marine mammal prey species. Monitoring will have to be species-, location-, and season-specific.

    Some work has already been done to identify and implement monitoring programs to collect data to drive the models. For instance, in 2008 the MMS funded a field study that attempts to broadly survey marine fish distribution and their assemblages in the Beaufort Sea, with concurrent collection of salinity, temperature, and plankton data. This work is expanding and will be integrated with multi-year studies of the Beaufort and Chukchi Seas.
    Work will be needed to develop integrated databases and to develop, validate, and apply prey species models.

  6. What will be the ecosystem level effects on shifts in the distribution and abundance of fish and other species?

    Investigating this should first involve the development of conceptual models that start with a single species and show interactions between species and their environment (e.g., a food web, augmented by known anthropogenic impacts). The conceptual model can be used to prioritize assessment and monitoring efforts. As for other questions, major metrics to monitor include seasonal abundance, distribution and movements of animals, and underlying causes of population dynamics. Climate monitoring will also be necessary for understanding historic and current ecology, and for predicting future scenarios. Eventual development of a quantitative ecosystem model would be beneficial.

  7. If fish species shift north, will fishing (including commercial fishing) patterns change and what will the effect be on management options and on non-target species?

    At this time, NMFS has largely prohibited commercial fishing in the federally-managed waters of the Arctic north of the Bering Strait. As such, there would not be a major shift in large commercial fisheries in federal waters in the foreseeable future even if the fish move dramatically north. Further, a shift of commercially-important fish to the north is not likely to substantially change commercial fisheries managed by the State of Alaska because there are no local processing options for fish on the North Slope and there are not likely to be large-scale state-managed fisheries in the foreseeable future.

    There is likely to be an increase in the subsistence harvest of commercially important fish as new species become available farther north. Because of the potential for subsistence harvest to affect commercial fish stocks, some understanding of changes in subsistence harvest of fish would be required. However, at this time, there are relatively few programs to monitor fish on the North Slope. The NSB monitors subsistence fisheries in North Slope villages and ConocoPhillips monitors subsistence fisheries in Nuiqsut, but additional details about such fisheries are needed. Traditional Ecological Knowledge will be key to understanding changes in subsistence harvest species and patterns.

  8. Will shipping affect whale migration and hunter access?

    At this time, there is limited information on whether and to what extent whale migration will be affected by changes in shipping. However, BP’s bowhead whale study around Northstar suggests that at least some whales will move away from or otherwise respond to low-level anthropogenic sounds, including those associated with routine vessel traffic. Shipping may have direct (e.g., ship strikes, avoidance of areas with high sound levels, or changes in calling behavior) or indirect (e.g., release of contaminants ingested by whales via lower tropic levels) impacts on whales. Studying the direct impacts will require more information on fine-scale movements of whales in response to received sound levels, improved reporting of ship strikes, and focused acoustics studies. This issue is of concern world-wide, so studies on similar marine mammal populations (e.g., right whales, humpback whales) may be directly relevant to what can be expected for bowhead whales.

    The Arctic Council recently completed the Arctic Marine Shipping Assessment (AMSA). The AMSA 2009 Report is posted at: http://arcticportal.org/pame/amsa. It provides the best compilation to date of current arctic marine shipping uses and is based primarily on a thorough analysis of arctic shipping in the year 2004. This 2004 database may serve as a baseline for future comparisons. To the extent that the information compiled in this report overlaps with NSSI agency missions and specific management concerns, there may be fertile ground for identifying shared priorities and opportunities for collaboration.

    There was specific concern in the discussion of this issue about routine assessments of the acoustic profile environment of all ships. Agencies involved in the NSSI may not have the ability to require that acoustics data be collected on all ships; vessels such as icebreakers and commercial barges may “fall through the cracks” because there may be no federal nexus to require measurements. The NSSI might specifically be able to help by encouraging that measurements of these vessels be collected. Standards for measuring the acoustic signatures of vessels must be developed, as the lack of standards currently precludes understanding comparisons between vessels.

    If shipping is likely to meaningfully impact whale populations, it might be preferable to use resources to focus on reducing the likely impacts of shipping in lieu of studying the impacts. For instance, technologies that could reduce vessel noise should be identified and/or investigated.

    To assess whether hunter access is being affected by shipping (or more broadly, by any perturbation), more data must be collected on hunter success and hunting patterns over time. It will be important to maintain a long-term database to monitor hunter access to subsistence resources and results of harvest attempts. MMS has a study under procurement that will attempt to accomplish this for communities in the Chukchi Sea, as well as the ongoing study on Cross Island.

  9. Can we identify species/habitat conservation refugia?

    Identification of important habitat that might require additional protection will be relatively easy to do for animals that are switching to a more terrestrial way of life (walrus/polar bears); this will be much harder to do for species that remain pelagic. The types of studies previously mentioned, including studies on distribution and movements of animals, will be needed to assess habitat use and changes in habitat use. It has been clear from studies of other animals (Steller sea lions, northern fur seals) that assessing habitat use can take many years, so if assessing changes in habitat use is critical to responsible management of species, a major commitment of resources will be necessary and results will likely not be immediately forthcoming. Some historical sources of information – such as that collected by BWASP and COMIDA surveys as well as data from historical accounts recorded by 19th and 20th century whalers – may provide information on where dense concentrations have occurred in the past. However, these (and other) data will be of most use if there is concurrent information on the oceanographic conditions that are likely causing the aggregations.

  10. What will be the metric of successful management in the future (for example, under ESA)?

    Both NOAA and the USFWS have very specific measures for whether management measures are successful for ESA-listed species (e.g., specific downlisting and delisting criteria, and specific actions called for in recovery plans). Management for ESA listed species is, of course, most successful when species are downlisted or delisted. However, arresting the decline and stabilizing the population of a listed species is also a measure of success, as is a measurable reduction in the factors that led to the species listing – for example, the elimination of an invasive species that contributed to the decline of the native listed species. Other possible measures for success are that current resource users continue to have the same access to the species at the same time that other stakeholders gain access to other resources, or that species are sufficiently abundant that traditional harvests are sustainable.

Recommendations:

  1. Develop an understanding of the data on marine mammals, their prey, current habitat use, current impacts of perturbations (climate, anthropogenic operations), and the subsistence harvest so that changes in current conditions can be measured or the causes of the changes identified.Priorities should be for species listed as endangered, threatened, or depleted; species where human-related mortality is suspected as the cause of a decline; or species that are the focus of a subsistence harvest. Despite the numerous and varied studies over the years, researchers lack baseline data at the appropriate temporal and spatial scales for many species. The NSSI can help by identifying the most important management questions to guide researchers towards projects and programs at the appropriate spatial and temporal scale.
  2. More long-term integrative studies, as typified by the MMS-funded “BOWFEST” and BP and ConocoPhillips’s Arctic cisco studies, are needed to understand why animals are distributed in particular ways. Ideally, carrying out such studies in the relative absence of anthropogenic impacts (i.e., with a defined pre-development baseline of ecosystem function) will be necessary to understand natural variation before a complete understanding of how changes in climate or anthropogenic effects can be assessed.
  3. Pursue studies that allow the assessment of cumulative impacts of multiple types of stressors (including climate change, contaminants, underwater sounds, and human-animal interactions) over multiple years.
  4. Consider using the partnership between the North Pacific Research Board and the National Science Foundation on integrated studies of the Bering Sea ecosystem (see: http://bsierp.nprb.org) as a model for the Arctic. The NSSI and its member agencies should explore potential collaborative opportunities with various organizations, including the North Pacific Research Board.
Click here to download the Marine Mammals and Their Prey Emerging Issue Summary in PDF format