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

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.

CPUE comparison of traditional crayfish fyke net rigged with knotted net and alternatively knotless net

In this study, it is aimed to compare the yield and strength of the crayfish fyke rigged with knotless net with 210d/12 rope thickness with those of the traditional net material rigged with 210d/6 knotted net which is widely used in Turkey in fishing crayfish (Pontastacus leptodactylus, Eschscholtz, 1823). The study was carried out on a monthly basis between June 2017 and May 2018. In the study, a total of 300 fyke nets, equipped with 150 classical and 150 alternative nets, were used. The caught crayfishes were measured and weighted according to the fyke net they were caught in. A total of 3509 crayfish were caught, 1465 of which were caught with alternative fyke net and 2044 with traditional fyke net. Average CPUE value ranged from 10.93 (g/fyke net/day) to 281.14 (g/fyke net/day) for per fishing operation. Average CPUE value of the traditional gear was found to be 98.34 (g/fyke net/day) , while that of the alternative gear was determined as 79.46 (g/fyke net/day), and no statistically significant difference was found between average CPUE values (p>0.05). Average strength value of the traditional fyke net was determined as (± SE) 10.43 ± 0.27 kg, while that value in 210d / 12 knotless net was identified as 14.50 ± 0.91 kg (p<0.05). Although it has high strength, since the CPUE value of the alternative fyke net is lower by 19.20% compared to the traditional gear, it is believed that its use in crayfish fishing will not be profitable.

Population structure, growth and reproduction characteristics of the portunid crab, Carcinus aestuarii Nardo, 1847 (Decapoda, Carcinidae) in Çardak Lagoon, Turkish Straits System

The aim of the present study was to determine the population structure and bioecological characteristics of the portunid crab, Carcinus aestuarii in Çardak Lagoon. In this study, the crabs were sampled by means of fyke-nets at 6 different stations between April 2015 and March 2016. A total of 2458 individuals (686 females, 1755 males, and 17 juveniles) were captured. The average carapace length was measured as 38.85 ± 0.17 mm in females, and 47.65 ± 0.16 mm in males. The highest number of specimens was observed in November with 239 individuals, while the lowest number (125 specimens) was observed in February. The reproductive period in both sexes was between November and February and females with eggs were found in November, February and March. An average number of eggs in a female was 61 390 ± 8.48 and the egg diameter was 345 μm. The female : male ratio was 0.39 : 1. This paper includes the first published data on population structure, growth, and reproduction characteristics of C. aestuarii in a protected lagoon in the Turkish Straits System.

Length–weight relationships comparison between juveniles and adults of fish species from the mangroves of south Brazil

This study reports the length‐weight relationships (LWRs) for 8 fish species that inhabit mangroves. Many fisheries depend on mangroves, which serve as nursery and feeding areas for the juvenile stage of fishes, shrimp, and other fishery resources. In this sense, mangroves provide many ecosystem services, therefore increasing the basic biological knowledge of these ecosystems can help to understand their functioning and create conservation strategies. The majority of LWR studies do not consider juveniles, and it is important to consider these differences as juveniles can grow differently from adults. The fishes were collected from Perequê mangrove, Paraná, Brazil between 2008 and 2010. A variety of fishery gears were employed, including trammel nets, fyke nets, and traps made with plastic bottles combined with four baits. The specimens were measured (weight and length), sexed and evaluated for maturational stage. For the adults, the LWRs were calculated separately by the sex, while juvenile LWRs were estimated together. In general, there were differences in growth type between sexes and life stages. Some species showed differences compared to FishBase estimations, but this could be due to the lengths (and life stage) of the individuals used in the present study compared to FishBase. The discrepancies between adult, juvenile and FishBase estimations showed the importance of considering these aspects in studies using LWR.

Evaluating the suitability of fyke nets for small-scale fisheries in the Free State Province of South Africa

South Africa is under increasing pressure to develop small-scale fisheries in inland waters. To inform appropriate development of this sector in the Free State Province, the catch rate of double-ended fyke nets was evaluated using survey data from 20 impoundments sampled during the 2013/2014 summer season. Fyke nets were set over night and the total sample effort was 114 fyke net nights. Overall catch per unit effort (CPUE) was 16.8 ± 28.3 kg·net-1·night-1 and catch composition was dependent on impoundment, but generally comprised of a mixture of common carp Cyprinus carpio, African sharptooth catfish Clarias gariepinus, smallmouth yellowfish Labeobarbus aeneus, Orange River mudfish Labeo capensis and moggel Labeo umbratus. The influence of temperature and the potential benefits of baiting the nets were subsequently evaluated through monthly sampling in the hyper-eutrophic Krugersdrift Dam and at the oligotrophic Gariep Dam. Baiting did not significantly influence CPUE, which was significantly higher at Krugersdrift Dam (19.97 ± 23.22 kg·net-1·night-1) than at Gariep Dam (5.02 ± 6.05 kg·net-1·night-1). Increasing temperature had a positive effect on CPUE at Krugersdrift Dam but not at Gariep Dam. Species composition also differed between impoundments and, as a result, we conclude that seasonal catch rates and species compositions will need to be evaluated prior to implementation of fyke net fisheries in specific localities.

The PPEAO experimental fishing dataset: Fish from West African estuaries, lagoons and reservoirs

This paper describes a dataset of fish, crustacean and mollusc occurrences extracted from the “Experimental Fishing” section of the IRD's PPEAO information system. PPEAO stands for “Fish communities and artisanal fisheries of West African estuarine, lagoon and freshwater ecosystems”. This database contains information collected using two different methods: experimental fishing and surveys of the artisanal fisheries that exploit these ecosystems. The database is accessible at http://ppeao.ird.fr. The current dataset is available on GBIF.org at 10.15468/ra4voa. It comprises the occurrences of 314 fish, crustacean and mollusc taxa collected in experimental sampling surveys of different aquatic ecosystems in West Africa between 1979 and 2013. Different types of fishing gear were used including purse seines, gill nets and fyke nets. The taxa were identified by IRD scientists or by scientific partners well trained in systematics. Most taxa were identified at species level (97% of cases). This dataset is the result of 213 fishing surveys, 5,362 fishing hauls and 31,709 occurrences (28,428 of fish taxa and 3,281 of crustaceans and molluscs). The number of individuals per species and per haul is included and 80% of occurrences are geolocated.

Ichthyofauna species composition comparison in two estuarine lakes: Ptasi Raj and Mikoszewskie located in the Natura 2000 site "Ostoja w Ujściu Wisły"

The purpose of the following studies was to get knowledge about the composition of the ichthyofauna of two estuarine lakes: Mikoszewskie and Ptasi Raj in the Natura 2000 area “Ostoja w Ujściu Wisły” (PLH220044), located within the delta estuary created by two channels of the Vistula river: Wisła Śmiała and Przekop Wisły, reaching the Gulf of Gdańsk. Despite the research conducted on the existing flora and fauna in both nature reserves, the ichthyofauna of the lakes has not been studied so far. In order to determine as completely as possible the taxonomic composition and the quantitative structure of ichthyofauna, the different fishing gear was used: fyke nets, NORDIC multimash survey gillnets, minnow traps. In Mikoszewskie lake, there were caught a total of 774 fish representing 17 species. Higher fish number in catches, with a comparable effort applied, were recorded on the Ptasi Raj lake, where a total of 2032 fish representing 16 species were captured. Out of all 26 species found, only 9 of them were found in both water reservoirs. As it transpires from the above data, both lakes, despite seemingly similar location, due to different hydrological conditions, clearly differ in terms of the structure of inhabiting ichthyofauna. Based on the analysis of the results of conducted fish catches, it can be concluded that the ichthyofauna of the Mikoszewskie Lake is characteristic for freshwater habitats, whereas in the waters of the Ptasi Raj lake, fish populations depend on a permanent connection with the estuary waters of the Wisła Śmiała channel.