Ilaria Martino, Daniel Li Veli, Andrea Petetta, Giorgio Vianson, Bent Herrmann, Roberto Cacciamani, Alessandro Lucchetti, Antonello Sala, Sepideh Jafarzadeh, Nurul Huda, Einar Skaftason, Finbarr G. O’Neill, Emilio Notti
Reducing fuel consumption, hydrodynamic drag and seabed impact without compromising catch performance and size selectivity remains a key challenge for demersal trawl fisheries. This study presents a comparison of demersal trawl configurations designed to reduce energy demand and improve the environmental performance of a Mediterranean bottom trawl fishery. The analysis focused on two configurations of the four-panel otter trawl design known as the “Americana”: a traditional commercial configuration and a newly optimised experimental design developed through targeted modifications in mesh size distribution, netting material and belly geometry. The two gears were first evaluated through flume-tank trials using 1:10 scale models. These tests showed that the experimental trawl achieved a wider horizontal geometry and substantially lower towing load than the traditional design, supporting the expected reduction in drag associated with the decrease in twine surface area and projected resistance. Full-scale sea trials were then conducted in the central Adriatic Sea, Italy, under comparable operational conditions. A total of 19 comparative hauls were carried out, alternating between the traditional and experimental configurations. Fuel consumption, vessel speed, towing loads at the winch and wing-ends, net geometry and GPS data were collected using a harmonised instrumentation system. Catch data were also recorded to assess changes in fishing performance, catch composition and size-dependent catch efficiency. A dedicated lift test was used to derive a vessel-specific speed -fuel consumption model and to partition total fuel use during towing into vessel-related and gear-related components. Compared with the traditional gear, the experimental trawl showed greater horizontal net spread and markedly reduced vertical opening. These changes resulted in a 26.7% reduction in hydrodynamic drag and a 15% decrease in fuel consumption during towing. When fuel use was partitioned, gear-related fuel demand showed an even larger relative reduction of 29.7%. Total catch rates did not differ significantly between gear configurations. Catch comparison analyses indicated species-specific responses, with higher catch efficiency for pelagic and semi-pelagic species and reduced retention of smaller individuals for some demersal species. Overall, the results demonstrate that targeted trawl modifications can improve energy efficiency and potentially reduce seabed interaction while maintaining commercially acceptable catch performance.
Topiltzin Contreras-MacBeath, Masiel Moreno Romero, Humberto Mejía Mojica, Juan Manuel Rivas González, Juan Carlos Sandoval Manríque, Juan Alberto Hernández Arias, Enrique González Gavito
Springs, as sensitive freshwater ecosystems, are particularly vulnerable to anthropogenic factors such as water extraction, pollution, and climate change. Las Estacas spring in Central Mexico, managed as a water park within a state reserve, serves as an ideal space for environmental education and conservation efforts. Snorkel surveys identified 14 fish species, with 70% being invasive and most of these come from ornamental fish. We computed multiple diversity indices and evaluated sampling completeness through rarefaction analysis. The fish assemblage was dominated by Xiphophorus helerii and Amatitlania nigrofasciata with 23% and 21% of the sample respectively, it exhibited moderate diversity (Shannon H’ = 1.955) with relatively even species distribution (Pielou’s J’ = 0.741). Rarefaction analysis confirmed adequate sampling effort, with the curve approaching asymptote at approximately 3,501 individuals (95% of observed richness). The findings provide baseline biodiversity metrics essential for conservation monitoring and ecosystem management. To address this, a rewilding project is now in place, with the goal to establish a fish assemblage dominated by native species through habitat management, exotic species control, native species introduction, and education.
Graciela Pulido Petit, Felipe Thomas, Oscar Brenes, María-Pía Beltrán, Rafaella Dueñas-Olvera, Hector Barrios-Garrido, Felix Morales
Coastal wetlands are vital habitats for elasmobranchs, yet the spatial ecology of many species remains poorly understood, hindering effective conservation. The Pacific chupare ray, Styracura pacifica, listed as Vulnerable by the IUCN, is one such data-poor species with virtually unknown feeding habits and limited ecological data. This study aimed to address the spatial ecology of S. pacifica within the Térraba-Sierpe National Wetland (HNTS), Costa Rica, providing baseline data for management. We employed a participatory science framework, integrating Local Ecological Knowledge (LEK) from artisanal fishers with over 15 years of experience in the area, to identify key sampling sites in the main river channel and intertidal sand flat pools. Data were collected between 2022 and 2023 using floating longlines and modified cast nets. For each captured ray, sex and disc width (DW) were recorded, alongside environmental variables like temperature and precipitation. Due to non-normal catch per unit effort (CPUE) distributions, non-parametric analyses were applied. Relationships between CPUE, disc width (DW), and environmental variables were assessed using Spearman correlations, and differences between ecosystems, years, and groups were evaluated using a rank-based test. A total of 66 individuals were captured across both habitats. Captures were exclusively composed of immature individuals, with significantly smaller DWs recorded in intertidal pools (19.6–37 cm DW) compared to the main channel (31-55.7 cm DW), confirming strong size-based habitat segregation. CPUE was significantly and inversely correlated with temperature in the main channel and with rainfall in the intertidal pools, suggesting dynamic shifts in distribution linked to local environmental conditions. Our findings provide empirical evidence that the HNTS functions as a crucial nursery system for juvenile S. pacifica. The observed sensitivity to temperature and rainfall highlights the vulnerability of these life stages to climate-driven habitat instability. Methodologies that allow us to track individuals and their movements, adapted to small-sized rays, are recommended for a better understanding of habitat use.
Olha Malysheva, Inna Hoch, Oleksii Khudyi, Jutta Jahrl, Kostiantyn Demianenko, Viktor Demchenko, Sergii Bushuiev, Joern Gessner, Arne Ludwig
This article reviews the historical population status of Ukrainian sturgeon populations, assesses the current wartime situation, and develops future conservation priorities. Today, Ukraine is one of the few places in Europe where sturgeon still spawn naturally along their traditional migration routes. The review considers ways to enhance the protection of these populations and the pivotal role of coordinated efforts against poaching and illegal trade. The current state and problems of ex situ measures for natural populations are discussed. The potential of sturgeon farming in aquaculture to reduce anthropogenic pressure on natural populations is also considered. The article concludes that Ukraine requires an in-depth review of the existing legislative framework, the restoration of natural spawning grounds and increased releases of juveniles in order to fully restore populations. The successful conservation and survival of sturgeons in Ukrainian waters would require comprehensive support from partner countries, particularly the European Union.
