Hurricane-induced dramatic decline and natural recovery of a vulnerable sportfish population: Shoal bass (Micropterus cataractae) in the Chipola River, Florida

Freshwater fishes are among the most biodiverse vertebrate groups and among the most threatened by anthropogenic activities. Many occur in small and geographically restricted populations that are increasingly subject to catastrophic events (hurricanes, wildfires, extreme floods and droughts), but it has rarely been possible to assess the impacts of such events. Here we document the decline and recovery of a regularly monitored, small shoal bass (Micropterus cataractae) population in the Chipola River, Florida following a catastrophic hurricane disturbance. The Chipola River population has the lowest level of interspecific hybridization (over 90 % non-introgressed shoal bass) within the species' range, a census population size of 2165 (95 % CI [1,383, 3,801]) in 2009 and a genetically effective population size N-e of 135 (95 % CI [70, 472]). In 2018, Hurricane Michael devastated the Chipola River and watershed. A survey conducted in 2019 indicated a severe decline (91 %) in relative population abundance and a very low N-e at 21 (95 % CI [16, 29]). However, the detection of young-of-year fish indicated that the depleted population had experienced successful reproduction. In fall 2021, the census population had recovered to 1039 fish (95 % CI [660, 1,814]) and Ne at 40 (95 % CI [31, 50]). While the population has shown considerable resilience in the face of hurricane disturbance, it remains vulnerable to future catastrophic events and may also suffer a long-term reduction in its adaptive potential due to a relatively low effective population size. To address these threats, continued monitoring is necessitated and targeted measures such as translocation of non-introgressed individuals from neighboring populations or establishment of a captive population of sufficient effective population size may be required to conserve the species in the long term.