Abstract
Marine mammals can play important ecological roles in aquatic ecosystems, and their presence can be key to community structure and function. Consequently, marine mammals are often considered indicators of ecosystem health and flagship species. Yet, historical population declines caused by exploitation, and additional current threats, such as climate change, fisheries bycatch, pollution and maritime development, continue to impact many marine mammal species, and at least 25% are classified as threatened (Critically Endangered, Endangered or Vulnerable) on the IUCN Red List. Conversely, some species have experienced population increases/recoveries in recent decades, reflecting management interventions, and are heralded as conservation successes. To continue these successes and reverse the downward trajectories of at-risk species, it is necessary to evaluate the threats faced by marine mammals and the conservation mechanisms available to address them. Additionally, there is a need to identify evidence-based priorities of both research and conservation needs across a range of settings and taxa. To that effect we: (1) outline the key threats to marine mammals and their impacts, identify the associated knowledge gaps and recommend actions needed; (2) discuss the merits and downfalls of established and emerging conservation mechanisms; (3) outline the application of research and monitoring techniques; and (4) highlight particular taxa/populations that are in urgent need of focus.
Highlights
Marine mammals, including 126 extant species of cetaceans, pinnipeds, sirenians, sea otters Enhydra lutris and polar bears Ursus maritimus known to date, can play important ecological rolesPublisher: Inter-Research · www.int-res.comEndang Species Res 44: 291–325, 2021 historical declines caused by exploitation, and additional current threats, such as climate change, fisheries bycatch, pollution and maritime development, continue to jeopardize many marine mammal species (Kovacs et al 2012, Magera et al 2013, Parsons et al 2015, Albouy et al 2017, Avila et al 2018)
Where monitoring is carried out, gaps in data on fishing effort, marine mammal encounter frequency, bycatch rates, species identification and the fate of animals post-capture and release limit our ability to assess the risk of fisheries bycatch, understand the cumulative impacts from fisheries that overlap with the distributions of individual populations and constrain management action (Hines et al 2020)
We suggest that the uptake of marine mammal conservation-focussed recommendations may benefit from considering how market incentives could aid in addressing the socio-economic impacts of regulatory or other measures whose consequences may impede conservation outcomes
Summary
Marine mammals, including 126 extant species of cetaceans (whales, porpoises and dolphins), pinnipeds (true seals, fur seals, sea lions and walruses), sirenians (dugongs and manatees), sea otters Enhydra lutris and polar bears Ursus maritimus known to date, can play important ecological roles. Endang Species Res 44: 291–325, 2021 historical declines caused by exploitation, and additional current threats, such as climate change, fisheries bycatch, pollution and maritime development, continue to jeopardize many marine mammal species (Kovacs et al 2012, Magera et al 2013, Parsons et al 2015, Albouy et al 2017, Avila et al 2018). We (1) outline key threats to marine mammals from anthropogenic activities, identify knowledge gaps and recommend responses; (2) discuss the merits and downfalls of existing and future conservation mechanisms; (3) outline the application of research and monitoring techniques; and (4) highlight particular taxa/populations that are in urgent need of focus Given that they make up the majority of this animal group, we generally focus on cetaceans and pinnipeds
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