Abstract
New information on weakfish introduction vectors, its invasive status, distribution, and use as a fishing resource arose after the publication of “The transatlantic introduction of weakfish Cynoscion regalis (Bloch & Schneider, 1801) (Sciaenidae, Pisces) into Europe” by Morais and Teodósio (2016). Currently, the first known report of weakfish in Europe dates back to September 2009, with a specimen captured in the Schelde estuary (Belgium/The Netherlands). This fact suggests that weakfish could have been introduced into Europe via multiple and independent ballast water introduction events, and not through a point-source introduction event with subsequent dispersion as previously hypothesized. It is also unlikely that Schelde weakfish migrated southwards to colonize Iberian aquatic ecosystems. Weakfish have established a population in the Gulf of Cádiz region and have already reached an invasive status in the Sado estuary (Portugal). Weakfish were also captured in several other locations along the Portuguese coast, including the Tagus and Mira estuaries at least since 2013 or 2014, and the Ria Formosa lagoon in 2017. Tagus anglers caught weakfish specimens of ~1 kg and ~40 cm in November 2016, which corresponds to fish of 3+ years of age in the native range. The presence of weakfish in the Tagus estuary is still fairly unknown to local anglers. Sado weakfish has already been sold in local fish markets in southern Portugal for 3 to 10 € kg−1. However, we consider that the weakfish sale price is underrated in comparison with other wild species (e.g., meagre, seabass, gilthead seabream). Increasing sale price will convince fishers to use weakfish as a new fishing resource; however, it is necessary to promote the species among consumers and evaluate consumers’ preference in respect to other species. A putative biological threat might turn into a new valuable fishing resource by implementing adequate management solutions.
Highlights
Identifying the introduction vectors and sites of introduction is critical for the enforcement of adequate management strategies, to eradicate a non-indigenous species, mitigate its impacts, and prevent further introductions
The role of citizen science was fundamental for Portuguese scientists in acknowledging the presence of weakfish in Portuguese aquatic ecosystems [2]
Here,Here, it was was proposed thatsubstantial the substantial reduction of the population of standing stock could only be proposed that the reduction of the population of standing stock could only be achieved achieved locally with intense fishing pressure across several consecutive years
Summary
Identifying the introduction vectors and sites of introduction is critical for the enforcement of adequate management strategies, to eradicate a non-indigenous species, mitigate its impacts, and prevent further introductions. It was hypothesized that weakfish were introduced in the Sado estuary (Portugal) before 2012, via ballast water, and that individuals dispersed northwards to the Galician coast as well as southwards to the Gulf of Cádiz [2]. News of weakfish capture in the Guadiana estuary in June 2016 continued to provide new reports [3,4], from both scientists [5,6,7] and Diversity 2017, 9, 47; doi:10.3390/d9040047 www.mdpi.com/journal/diversity. Europe is crucial to avoid the perpetuation of erroneous information, to set new hypotheses, and to propose new management solutions. The introduction of fish species via ballast water is uncommon, yet multiple independent introductions have been documented (Table 1). A few Gobiidae and Blenniidae species provide examples of such cases (Table 1), probably because of their crevicolous nature [13] and other biological traits that allow individuals to withstand long transport periods (e.g., larvae with large yolk-sacs)
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