Raising the flag on marine alien fouling species

Abstract

Harbours are known introduction foci of marine alien species. They act as recipients of new introductions and as sources for regional spread. We report on subtidal surveys of fouling communities from 14 harbours along the coastline of South Africa that were used to identify predictors of high alien species numbers in support of prioritisation of monitoring actions by authorities. The harbours varied in nature from large, international shipping hubs to small, regional fishing harbours and recreational marinas. Fouling assemblages were assessed using visual and scrape sampling to ensure the detection of large, mobile and small inconspicuous species. In total, 29 alien species were recorded, 15 of which were detected outside of their previously known ranges. The number of species recorded per harbour varied from five to. Results revealed that high numbers of alien species were associated with the presence of yachts and low primary productivity. Harbours which had yachts and occurred in areas with mean Chl a minimum levels lower than 0.21 mg.m -3 had the highest number of alien species, while harbours without yachts that were larger than 0.1km 2 supported the fewest alien species. These findings suggest that the presence of yachts can be used to identify harbours with high numbers of alien species, particularly in regions with low productivity. While the applicability of these findings to other regions remains to be tested, this work suggests that harbours that fall within this category could be prioritised for monitoring of marine alien species.

Compared stress tolerance to short-term exposure in native and invasive tunicates from the NE Atlantic: when the invader performs better

“…This study is among the first 23 to experimentally determine limits for temperature and hyposalinity stress for either species and 24 supports the hypothesis that the invader performs better under extreme conditions. Future Evidence supports the hypothesis that shipping and hull fouling is a major vector in transporting 39 marine species worldwide (Clarke Murray et al 2012;Peters et al 2017). What is less clear is the 40 mechanisms employed by invasive species to enable them to become so pervasive.…”

Coastal Invasions: The South African Context

“…Nonetheless, extensive research on rocky shores in KwaZulu-Natal (e.g. Sink et al 2005), and recent surveys of harbours between Mossel Bay and Richards Bay (Peters et al 2017) failed to detect new marine alien species, suggesting that other factors may be at play. A second explanation may relate to differential vector strength along the coast.…”

“…Although shipping can also be responsible for secondary spread, the pathway takes on a slightly different nature at a regional scale, as large commercial vessels become less important, and small and recreational vessels become more important (Clarke-Murray et al 2011). In South Africa, fouling on recreational yachts was recently linked to the regional spread of marine alien species (Peters et al 2014(Peters et al , 2017, with the Japanese Skeleton Shrimp, Caprella mutica offering an example of a newly-introduced species that has been moved at a regional scale (Peters and Robinson 2017). Although only recreational yachts have been investigated as a mechanism of intra-regional species transfer, it is likely that other regional vessels such as tour boats and fishing boats also play a role, but this remains to be quantified.…”

“…Reflecting this, an additional five alien species [the intertidal isopod Ligia exotica (Greenan et al 2018), the Chilean Stone Crab Homalaspis plana (Peters and Robinson 2018), the South American Sunstar Heliaster helianthus (Peters and Robinson 2018), the Maritime Earwig Anisolabis maritima (Griffiths 2018) and the barnacle Perforatus perforatus (CL Griffiths pers. comm)], as well as two invasive species [the amphipod Caprella mutica (Peters and Robinson 2017) and the porcelain crab Porcellana africana (Griffiths et al 2018)] have been recorded since 2016.…”

“…Since that time there has been an increased focus on experimental studies (both laboratory and field-based) and an emphasis on understanding biological interactions (e.g. Steffani and Branch 2003;Zardi et al 2006;Branch et al 2008Branch et al , 2010Bownes and McQuaid 2010) and intra-regional spread (Peters et al 2017).…”