Intensive Fishing Effort and Market Controls as Management Tools for Invasive Aquatic Species: A Review

Invasive aquatic species may disrupt ecosystems and cause socioeconomic damage. Biosecurity protocols were developed to prevent transport and unintended introductions of invasive species, but less attention has been paid to management once they become established. The use of classical fisheries stock assessment to determine levels at which selectively targeted fisheries elicit recruitment overfishing is discussed. Case studies of several species of invasive aquatic organisms, including lionfish Pterois spp. two species of mytilids and three species of crayfish, including Faxonius rusticus (Girard, 1852), are discussed as examples. Fecundity as measured by egg production rate (EPR) is a key factor determining how the various species react to fishing pressure. Ecosystem modelling of predatorprey relations between indigenous and invasive aquatic species suggests that restricting fishing effort on indigenous predators of invasive prey may be as effective in managing invasive species in lieu of directly increasing fishing effort on the targeted species itself. Invasive mytilids Dreissena polymorpha (Pallas, 1771) and Mytella strigata (Hanley, 1843) may not be effectively controlled by intensive fishing effort due to high EPR values. However, crayfish that brood offspring and exhibit much lower EPR values may be ideal candidates for stock assessment and setting fishing effort targets to promote recruitment overfishing. Recommendations for managing invasive aquatic species include: collecting data on population dynamics of the invasive species; assessing predator populations; developing fisheries that target the invasive species; and collecting socioeconomic data to understand the human dimensions of the impacts of the invasive species and inform subsequent policy development.

The Procambarus clarkii (red swamp crayfish) in Merja Zerga wetland in Morocco: Dynamic and impacts on aquatic vegetation

Procambarus clarkii, one of the most invasive aquatic species in the world, is present in the Mediterranean estuarine regions. The invasion of this species in these wetlands has a multitude of impacts, including the impact on flora. This study examines the floristic diversity and abundance of Procambarus clarkii in this wetland, as well as whether the presence of this aquatic species affects the flora. The Procambarus clarkii sampling lasted three years (2016, 2017, 2018) in the Merja zerga wetland, using fishermen’s boats. Vegetation sampling was conducted during the same Procambarus clarkii capture period to assess the abundance of Procambarus clarkii at the same time and recover the effect of this aquatic species on the flora. To strengthen our study a survey was conducted among sinners to assess the impacts of Procambarus clarkii in its living environment. The results showed that there was a significant difference in the abundance of Procambarus clarkii sampled over the years (2016, 2017, 2018). The floristic diversity of the Merja zerga lagoon is very important. The effect of Procambarus clarkii on the flora was very remarkable. Thus, the floristic species exposed to this impact are the species of genus Potamogéton. These results show that Procambarus clarkii can be considered as a factor contributing to the decline of the floristic diversity of the aquatic areas where it lives.