A Comparison of Traditional and Locally Novel Fishing Gear for the Exploitation of the Invasive Atlantic Blue Crab in the Eastern Adriatic Sea

Abstract

The Atlantic Blue Crab Callinectes sapidus has been recognized as invasive in the Mediterranean Sea, where it now provides a significant contribution to artisanal fisheries. In this study, we compared the efficiency, selectivity, and productivity of American wire crab traps and traditional fyke nets for the capture of Blue Crabs in a study conducted from June to December 2019 in the Parila Lagoon (River Neretva Estuary, Croatia). A total of 7707 specimens were caught in 15 wire traps, comprising 6959 males and 749 females. The total catch using 50 traditional fyke traps was 1451 crabs, of which 1211 were males and 240 were females. In general, wire crab traps showed a higher capture selectivity and economic performance compared to fyke nets. The catch per unit effort (CPUE) was 102.76 kg for the American wire crab trap and 5.96 kg for the traditional fyke net. The CPUE of gravid female Blue Crabs was lower for the wire traps than the fyke nets. Herein, the utility of crab traps as selective fishing gear for the capture of Blue Crabs, and management tools for control of the reproductive and recruitment phases of the crab, are discussed, with the perspective of future exploitation of the species as a commercially valuable shellfish product in the Mediterranean.

The Historical Trends and Recent Collapse of European Eel, Anguilla anguilla Fishery in the Neretva Estuary (Eastern Adriatic, Croatia)

“…The trend in eel catches was almost stable during this period, with the exception of the last three years, which showed a decline. Fishermen attributed this decline to the significant increase in the population of Atlantic blue crab in Parila Lagoon, previously also described [9].…”

“…have already been mentioned. More recently, the greatest threat is the increase in invasive and competing species, particularly the Atlantic blue crab and Largemouth bass [8,9,11].…”

“…The later period from 1970 to 2015 and to the present followed a similar trend of declining catches in the commercial (fall-winter) fishery [5]. More recently, the threat to local eel populations has been exacerbated by the tremendous increase in invasive species such as Largemouth bass (Micropterus salmoides) in freshwater areas [8] and Atlantic blue crab (Callinectes sapidus) in brackish water ecosystems [9]. which either feed on or compete with eels for food.…”

“…Due to increased controls by state institutions since 2020, the number of fishing gears used for recreational fishing (mainly small eel traps) has decreased significantly, but due to the high eel price, the fishing effort is still enormous, although eel catches are decreasing and the catch size is mostly 50-100 grams (Glamuzina et al, 2022). The number of eels under 30 grams has also declined significantly due to invasive species such as Largemouth bass in Kuti Lake [8] and blue crab in brackish water ecosystems [9] which either feed on or compete with eels. Figure 2 provides a historical overview of European eel catches in the Neretva estuary from 1930 to the present, highlighting the differences between the pre-and post-land reclamation periods.…”

The study of European eel, Anguilla anguilla in the RiverNeretva estuary (Eastern Adriatic Sea, Croatia) using traditional fishery gear

“…This was recently enhanced with an establishment of the strong population of invasive blue crab, Callinectes sapidus and its competition for the food and shelter with native crab and fish species (MANCINELLI et al, 2016), as well as new and invasive fish species records (GLAMUZINA et al, 2017;GLAMUZINA et al, 2021a). The blue crab significantly impacted the estuarine environment and species composition (GLAMUZINA et al, 2021b) and preyed on similar prey consumed by European eel in this ecosystem (MOROVIĆ, 1970). In the freshwater ecosystems the establishment of the largemouth bass, Micropterus salmoides population, and its invasive potential (GLAMUZINA et al, 2021a) through competition for the food with native eel, should produce similar negative effects as the blue crab in a brackish environment.…”