Design and testing of a trap removing Chinese mitten crabs (Eriocheir sinensis, H. Milne Edwards, 1853) from invaded river systems

Abstract

The Chinese mitten crab is one of the top invasive species in Europe. In Flanders (Belgium), they are associated with river ecosystem degradation, especially the loss of aquatic vegetation and associated ecosystem services. Management measures have therefore been put in place to reduce the number of crabs migrating between the sea and freshwater areas and ultimately control the population. Although we are still long way from the goal, a low‐cost method has been applied to successfully catch migrating crabs. In this article, we outline the design and functioning of the trap. We monitored the population in a lowland river, measured migration speeds and calculated crab densities. With over 1 million crabs caught in 2 years, the trap proved to be very effective. Median anadromous (spring) and catadromous (autumn) migration speeds were 0.69 and 0.96 km day−1, respectively. Anadromous migrating crab density was calculated to be up to 3.20 ind. m−2 river bed. Resident crab density was calculated to be up to 2.05 ind. m−2 river bed. We conclude that this trap is a very useful tool for water managers to catch Chinese mitten crabs in rivers and discuss the pathways towards reducing the population and protect the entire freshwater catchment.

The Use of Barriers to Limit the Spread of Aquatic Invasive Animal Species: A Global Review

“…In Europe (11 studies), AIS exclusion barriers have largely targeted invasive crayfish (e.g., Dana et al, 2011;Frings et al, 2013;Kerr et al, 2020;Krieg et al, 2021). Apart from crayfish studies, vertical barriers have also been tested to limit the spread of European minnow (Phoxinus phoxinus) in Scandinavia (Holthe et al, 2005), an innovative trap has been designed to intercept Chinese mitten crab (Eriocheir sinensis) as they migrate through a fish pass in Belgium (Schoelynck et al, 2020), and electric barriers have been used to protect endangered populations of endemic Mediterranean trout (Salmo cettii) from introduced brown trout (Salmo trutta) in Italy (Sabatini et al, 2018).…”

“…Velocity barriers (e.g., sloping weirs that create localised high current velocity zones) can be useful in preventing movement of AIS where they lack the locomotive ability to move upstream, although their efficiency has only been tested under laboratory conditions thus far (Frings et al, 2013;Kerr et al, 2020). Physical traps have been integrated with fish passes and function by capturing jumping fish only (Stuart et al, 2006) or by intercepting crawling crustaceans (Schoelynck et al, 2020). The other type of physical barrier which has been widely used are exclusion screens and nets, which aim to intercept larger-bodied invasive fish, although they are generally ineffective for early life stages (Martinez and Foreman, 2001;Hillyard et al, 2010;Tempero et al, 2019).…”

“…An advantage of physical barriers is that they tend to last longer term (multiple decades), although traps and screens require regular maintenance (Daniel et al, 2014). The majority of physical barriers are designed to prevent upstream passage only, with the exception of some bidirectional exclusion screens and traps (e.g., Tempero et al, 2019;Schoelynck et al, 2020).…”

Een kennisoverzicht van de Chinese wolhandkrab: naar een geïnformeerd beheer van wolhandkrab in Vlaanderen

“…Een aantal dergelijke installaties zijn reeds operationeel, of gepland (Tabel 1). De sleufval op de Kleine Nete te Grobbendonk (Antwerpen) wordt in detail beschreven door Schoelynck et al (2021). Deze auteurs testten ook de effectiviteit ervan tijdens 2018 en 2019, en dekten aldus twee op-en twee afwaartse migratiegolven af.…”

Invasieve Exoten in Vlaanderen: toestand en beleidsaanbevelingen: achtergrondrapport bij het Natuurrapport 2020

“…Daarom werden op strategische plaatsen, zoals de site van 's Hertogenmolens op de Demer te Aarschot, geleidingssystemen met valkuilen voorzien om deze overlast te beperken (ANB & INBO, 2016). Ondertussen werd door de Vlaamse Milieumaatschappij een krabbensleuf ontwikkeld en voorzien op de Kleine Nete in Grobbendonk waar in 2018 en 2019, vooral tijdens de voorjaarse, stroomopwaartse migratie van maart tot mei, meer dan een miljoen krabben werden gevangen (Schoelynck et al, 2020). Deze valsystemen zijn wellicht een geschikte monitoringtool maar de impact van het verwijderen van krabben op de populaties in stroomopwaartse delen van de rivier en in het estuarium is nog niet gedocumenteerd.…”