Population control to mitigate the spread of marine pests: insights from management of the Asian kelp Undaria pinnatifida and colonial ascidian Didemnum vexillum

Abstract

In June 2012 a single non-native snakehead fish was captured by local officials in a small pond within an urban park in Burnaby, British Columbia. This single snakehead fish garnered significant attention in the local and national media. DNA analysis determined it to be a blotched snakehead (Channa maculata) or possibly a hybrid; a warm water species native to China and Vietnam which is commonly sold in the live food fish trade, and occasionally kept by hobbyists. By collecting prey items from the pond and snakehead specimens from fish markets we used a novel stable isotope approach to estimate how long it had been since the snakehead had been released into the pond. Using a diet-switching tissue turnover model, we estimated that the snakehead was in the pond between 33 and 93 days. Subsequently, provincial legislation was amended to ban all species of snakehead fish, as well as numerous other potentially invasive fish and invertebrate species.

The putative impacts of the non‐native seaweed Sargassum muticum on native communities in tidepools of Southern California and investigation into the feasibility of local eradication

“…Here, sustained mechanical removal over a long period was successful in reducing recovery of an isolated population, but unsuccessful at locations where repeated introductions occurred (Hunt et al . ; Forrest & Hopkins ). Another key component in eradication considerations is the proximity to other invader populations near the eradication location, assuming eradication efforts are somewhat localized.…”

“…In New Zealand, the non‐native kelp Undaria pinnatifida was removed mechanically, with additional trials of heat and chemical treatments to target the microscopic gametophyte stage (Hunt et al . ; Forrest & Hopkins ). Here, sustained mechanical removal over a long period was successful in reducing recovery of an isolated population, but unsuccessful at locations where repeated introductions occurred (Hunt et al .…”

Drivers and pressures – Untangling the terms commonly used in marine science and policy

“…Therefore the consistent use of terminology is essential for efficient communication of scientific advice and appropriate managerial response. Clear differentiation between the 'pressure' and 'impacts' as well as understanding of the major operating driving forces, can help to strategically focus the effort on prevention of new invasions and mitigation of their spread rather than eradication of the already established NIS (costly and seldom effective measure; Piola et al, 2009;Forrest and Hopkins, 2013).…”

Some Bryozoa species recently introduced into the Azores: reproductive strategies as a proxy for further spread

“…Control of population levels, that is, to keep the species at an abundance level which is below a density-dependent adverse effect, or to contain or reduce the spread of target organisms, may be a more attainable goal than eradication for the management of non-indigenous species [31,43,60,79,92]. There are three main methods to keep an introduced species at low levels: (1) physical and mechanical control, often highly effective but labour-intensive [80]; (2) chemical control, sometimes effective but often controversial [80] and (3) biological control, considered arguable because many introduced species' enemies never become established [88], nontarget impacts occasionally occur [22] or biological control agents may spread to distant areas where they are unwanted [80].…”