The survival of hatchery‐origin pinto abalone Haliotis kamtschatkana released into Washington waters
Henry S. Carsona b✉, Dana J. Morinc d, Joshua V. Boumae f, Michael Ulricha b, Robert Sizemorea b
- aWashington Department of Fish and Wildlife Fish Management Division Olympia Washington USA
- bWashington Department of Fish and Wildlife, Fish Management Division, Olympia, Washington, USA
- cCooperative Wildlife Research Laboratory Southern Illinois University Carbondale Illinois USA
- dCooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, Illinois, USA
- ePuget Sound Restoration Fund Bainbridge Island Washington USA
- f
Papers open inside SciRah from the original publisher or repository; SciRah never hosts them.
Abstract
Abstract Wild populations of pinto abalone (Haliotis kamtschatkana) in Washington State have declined by 97% since 1992, despite a fishery closure since 1994. No recruitment has been detected recently, indicating probable reproductive failure due to low densities. A pilot programme placed a total of over 11,000 hatchery‐origin juveniles, age 18–22 months, at 10 sites in the San Juan Islands. Observed (naive) year 1 survival averaged 10.2% (0–23% range) and was most influenced by site compared with lineage or size‐at‐outplant. Families survived in the approximate proportions that they were outplanted, and there was little support for an effect of size‐at‐outplant on survival. Detection was low due to the small chance of sighting individuals on complex substrate. When derived from repeated sampling, an upper bound on naive detection rate averaged 0.38 and increased with size. When derived from a closed capture–recapture model, average detection was estimated at 0.19. Growth was highly variable and confounded with detection, but an average 3.4% of detected outplants across all sites (0–7.5% range) had reached reproductive size in 2017. A state‐space model of exponential population growth was modified to account for imperfect detection and yielded an estimated density of abalone for each survey. Seven out of eight sites included in the model remained above a target abalone density of 0.3 m−2 throughout the project. The majority of tagged abalone made little net movement over weekly and annual timescales, although some emigration likely reduced survival estimates. The restoration programme is transitioning from a pilot phase to a production phase, including optimization of hatchery and outplant processes. Existing well‐performing sites will receive additional cohorts every 4–5 years to maintain aggregation densities. New sites will replace poorly performing ones, although this is hampered by a poor understanding of the mechanisms behind site performance.
TL;DRThis study highlights the need to understand more fully the rationale behind the rapid decline in the number of bald eagles in Washington state over the past 50 years. (Semantic Scholar)