Abstract
Non-native fish introductions are a major threat to biodiversity and fisheries, and occur through numerous pathways that vary regionally in importance. A key strategy for managing invasions is to focus prevention efforts on pathways posing the greatest risk of future introductions. We identified high-risk pathways for fish establishment in the Mid-Atlantic region of the United States based on estimates of relative probability of establishment among pathways and records of previous introductions, which were considered in the context of emerging socioeconomic trends. We used estimates of propagule pressure, species’ environmental tolerance, and size of species pool to assess the risk of establishment by pathway. Pathways varied considerably in historic importance and species composition, with the majority of species introduced intentionally via stocking (primarily for sport, forage, or biocontrol) or bait release. Bait release, private stocking, illegal introductions intended to establish reproducing populations (e.g., of sport fish), aquaculture, and the sale of live organisms all create risks for future invasions in the Mid-Atlantic region. Of these pathways, bait release probably poses the greatest risk of introductions for the Mid-Atlantic region because propagule pressure is moderate, most released species are tolerant of local environmental conditions, and the pool of species available for transplantation is large. Our findings differ considerably from studies in other regions (e.g., bait release is a dominant pathway in the Mid-Atlantic region, whereas illegal introduction of sport fish is dominant in the western US and aquarium releases are dominant in Florida), demonstrating the need for regional-scale assessments of, and management strategies for, introduction pathways.
Highlights
Acanthaster planci (Linnaeus, 1758), the crown-ofthorns seastar, are voracious, opportunistic carnivores that typically consume sessile invertebrates, hard corals, and carrion
One lesson from invasion ecology readily applied to A. planci is the understanding of critical stages in life-history to inform cost-effective management actions and determine outbreak triggers (Pratchett et al 2014)
The long term prospects for the Great Barrier Reef are of concern without a dedicated long-term framework to target the higher risk, quick return impacts affecting coral cover during A. planci boom periods as well as monitoring and understanding the conditions needed to support bust cycles
Summary
Acanthaster planci (Linnaeus, 1758), the crown-ofthorns seastar, are voracious, opportunistic carnivores that typically consume sessile invertebrates, hard corals, and carrion. A. planci has exhibited long-term boom-bust population cycles to devastating effect in the Indo-Pacific, threatening the Great Barrier Reef (e.g., Uthicke et al 2009; Baird et al 2013). On the Great Barrier Reef there have been four documented A. planci outbreaks since the 1960’s, each spaced ~17 years apart (Pratchett et al 2014). During these outbreaks natural densities increase to a point resulting in “plagues” of the seastar consuming coral faster than it can grow.
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