Marine mammal conservation: over the horizon

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.

Asset Tracking Whales—First Deployment of a Custom-Made GPS/GSM Suction Cup Tag on Migrating Humpback Whales

“…Suction cup tags do not have to penetrate the animals' skin and can be used for short term deployments (hours to days), making them applicable for fine scale habitat use studies that investigate movements within the range of meters to kilometers. Information on fine scale habitat use of cetaceans can provide important insights into habitat preferences and sensitivity to environmental drivers (hydrodynamics, temperature gradients, salinity, bathymetry) as well as anthropogenic impacts [12,14]. The study of habitat use also plays an important role for conservation management in the light of increasing anthropogenic impacts in coastal habitats.…”

Science Alone Won’t Do It! South Africa’s Endangered Humpback Dolphins Sousa plumbea Face Complex Conservation Challenges

“…The urgency of the situation of Indian Ocean humpback dolphins off South Africa -and in fact with many other cetacean populations around the globe (e.g., Desforges et al, 2018;Nelms et al, 2021) highlights the need to abandon the "sentinel" concept (Fox, 2001;Reddy et al, 2001;Wells et al, 2004) and rather recognise cetaceans as "indicators" of ocean health, encompassing definitions of health on the individual level as well as at the population level (i.e., including connectivity, genetic diversity, and population size), thus reflecting a more holistic approach to health (Figure 3). While cetaceans have been used as indicator species when examining the potential impact of noise (Merchant et al, 2018), further studies considering cetaceans as indicators of cumulative impacts and thus the overall state of ocean health are needed.…”

“…The rapid global decline in biodiversity is evident in marine ecosystems (Sala and Knowlton, 2006), with an associated loss in important ecosystem services (Worm et al, 2006). Small cetaceans are not exempt from this trend and an increasing number of species and populations are of conservation concern (Jefferson, 2019;Nelms et al, 2021).…”

A decision support tool for integrated fisheries bycatch management

“…Some species of chondrichthyans (sharks, rays and chimaeras), marine turtles, sea snakes, marine mammals, seabirds and teleosts are threatened with extinction due to bycatch (Wallace et al 2013;Davidson et al 2015;Phillips et al 2016;Gray and Kennelly 2018;Dias et al 2019;Lopez-Mendilaharsu et al 2020;Nelms et al 2021;Pacoureau et al 2021). Depending on a fishery's management framework and markets, some of these species may be targeted, retained incidental catch (including retention of shark fins and manta and devil ray gill plates and discarding of the remaining carcass) or discarded (Elfes et al 2013;Cao et al 2014;O'Malley et al 2016;Dulvy et al 2017;Hall et al 2017).…”