Habitat compression and ecosystem shifts as potential links between marine heatwave and record whale entanglements

Abstract

Climate change and increased variability and intensity of climate events, in combination with recovering protected species populations and highly capitalized fisheries, are posing new challenges for fisheries management. We examine socio-ecological features of the unprecedented 2014-2016 northeast Pacific marine heatwave to understand the potential causes for record numbers of whale entanglements in the central California Current crab fishery. We observed habitat compression of coastal upwelling, changes in availability of forage species (krill and anchovy), and shoreward distribution shift of foraging whales. We propose that these ecosystem changes, combined with recovering whale populations, contributed to the exacerbation of entanglements throughout the marine heatwave. In 2016, domoic acid contamination prompted an unprecedented delay in the opening of California's Dungeness crab fishery that inadvertently intensified the spatial overlap between whales and crab fishery gear. We present a retroactive assessment of entanglements to demonstrate that cooperation of fishers, resource managers, and scientists could mitigate future entanglement risk by developing climate-ready fisheries approaches, while supporting thriving fishing communities.

Entanglement rates and haulout abundance trends of Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lions on the north coast of Washington state

“…In summer 2014, high sea surface temperatures associated with the warm anomaly referred to as “the Blob” reached the coast, causing the shortest upwelling season for the northern California Current on record [ 72 ], the impacts of which were seen well into 2016 [ 73 ]. Both California and Steller sea lions exhibited high rates of entanglement in our study area in 2014 and 2015, and 2014–2016 were also years of elevated large whale entanglements in the area [ 17 , 74 ]. It is possible that these anomalous ocean conditions changed the distribution of fishing effort, entangling materials, and prey items important to cetaceans and pinnipeds, causing habitat compression and contributing to the high levels of entanglement seen for both taxa.…”

Climate Extreme Seeds a New Domoic Acid Hotspot on the US West Coast

“…Small vessel fishers may trade their fishing effort disproportionately to access other fisheries when the crab season is canceled, causing concern for resource managers (Saez et al, 2020). Climate change and related warming have compressed habitats for many organisms (Santora et al, 2020). Both habitat compression and intensified Pseudo-nitzschia HABs with range expansion are a result of anomalously warm temperatures in the coastal ocean.…”

“…Entanglements of mostly humpback whales (Megaptera novaeangliae), were an indirect result of the 2015 HAB event because the delay of the crab season opener resulted in higher numbers of crab pot lines than usual along the whale migration routes (NOAA Fisheries, 2018;Saez et al, 2020;Santora et al, 2020). A record number of illnesses and deaths of marine mammals (McCabe et al, 2016) and seabirds (Piatt et al, 2020) were caused both by food web transfer of HAB toxins (McCabe et al, 2016) and habitat compression into a geographically reduced coastal zone of food availability (Santora et al, 2020).…”

“…Entanglements of mostly humpback whales (Megaptera novaeangliae), were an indirect result of the 2015 HAB event because the delay of the crab season opener resulted in higher numbers of crab pot lines than usual along the whale migration routes (NOAA Fisheries, 2018;Saez et al, 2020;Santora et al, 2020). A record number of illnesses and deaths of marine mammals (McCabe et al, 2016) and seabirds (Piatt et al, 2020) were caused both by food web transfer of HAB toxins (McCabe et al, 2016) and habitat compression into a geographically reduced coastal zone of food availability (Santora et al, 2020). An analysis of the historical record of large-scale Pseudonitzschia HABs has demonstrated that these events tend to occur during periods of anomalously warm ocean conditions such as El Niño, positive phases of the Pacific Decadal Oscillation (PDO), or the record-setting marine heatwave (McCabe et al, 2016;McKibben et al, 2017).…”

The Continuum of Northeast Pacific Marine Heatwaves and Their Relationship to the Tropical Pacific

“…The most prolonged MHW of the past 70 years, occurring during 2013–2015, covered a broad region of the Northeast Pacific, with local maximum warming of 2.8°C (Bond et al., 2015; Di Lorenzo & Mantua, 2016), and did not end until after the development in the tropics of a strong El Niño. Its ecosystem impacts were unprecedented, including massive stranding, entanglement, and mortality of marine species and seabirds (Cavole et al., 2016; Jones et al., 2018; Santora et al., 2020) and prolonged harmful algal blooms that closed major fisheries (McCabe et al., 2016; Ryan et al., 2017; Sanford et al., 2019). This record‐breaking event led to enhanced scrutiny of many Northeast Pacific MHW aspects (Frolicher & Laufkotter, 2018; Holbrook et al., 2020), including their severities (Hobday et al., 2016; Jacox et al., 2020; Scannell et al., 2016), tropical and extratropical driving mechanisms (D. J. Amaya et al., 2020; Bond et al., 2015; Di Lorenzo & Mantua, 2016; Holbrook et al., 2019), and predictability (Hu et al., 2017; Jacox et al.…”