Open AccessNon‐trophic impacts from white sharks complicate population recovery for sea otters
Author(s) -
Moxley Jerry H.,
Nicholson Teri E.,
Van Houtan Kyle S.,
Jorgensen Salvador J.
Publication year - 2019
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.5209
Subject(s) - carcharias , otter , kelp forest , keystone species , ecology , predation , biology , trophic cascade , apex predator , fishery , rookery , population , ecosystem , trophic level , kelp , mesopredator release hypothesis , food web , demography , juvenile , sociology
Complex interactions between protected populations may challenge the recovery of whole ecosystems. In California, white sharks ( Carcharodon carcharias ) mistargeting southern sea otters ( Enhydra lutris nereis ) are an emergent impact to sea otter recovery, inhibiting the broader ecosystem restoration sea otters might provide. Here, we integrate and analyze tracking and stranding data to compare the phenology of interactions between white sharks and their targeted prey (elephant seals, Mirounga angustirostris ) with those of mistargeted prey (sea otters, humans). Pronounced seasonal peaks in shark bites to otters and humans overlap in the late boreal summer, immediately before the annual adult white shark migration to elephant seal rookeries. From 1997 to 2017, the seasonal period when sharks bite otters expanded from 2 to 8 months of the year and occurred primarily in regions where kelp cover declined. Immature and male otters, demographics most associated with range expansion, were disproportionately impacted. While sea otters are understood to play a keystone role in kelp forests, recent ecosystem shifts are revealing unprecedented bottom‐up and top‐down interactions. Such shifts challenge ecosystem management programs that rely on static models of species interactions.