Invasion status of the common carp Cyprinus carpio in inland waters of Argentina

Impacts of environmental flow regulation on survival of aquatic organisms: a case study of Cyprinus Carpio in Baiyangdian, China

Decreasing water volume and increasing pollutants in wetlands pose challenges to aquatic life. While environmental flow regulation is widely applied to enhance aquatic habitats, its effectiveness needs to be evaluated. In this study, a hydrodynamic-water quality model was used to simulate the fields of flow, temperature, and pollutants. The Ecological Niche Modeling at the MetaLand EcologyLab (ENMTML) was utilized to evaluate the area of suitable habitats for aquatic organisms under both environmental flow regulation and no environmental flow regulation conditions. The typical Baiyangdian Wetland in northern China was taken as the study area, and the important economic fish, Cyprinus carpio, served as the indicator of aquatic species. The effectiveness of environmental flow regulation was evaluated from December 1, 2017, to June 30, 2018. The results indicated that the variables of water depth, dissolved oxygen (DO), ammonia nitrogen (NH4+-N) and Chlorophyll a (Chla) were the major environmental factors determining the variability of the suitable habitat area for Cyprinus carpio. The environmental flow regulation capacity of the Baiyangdian Wetland was 2.6 [Formula: see text] 108 m3, which produced a suitable habitat area of 135.538 km2 at the end of the water supply period. Compared with the no environmental flow regulation condition, the highly and moderately suitable habitat areas for Cyprinus carpio were enlarged by 56.30 km2 and 34.11 km2, respectively. The outcome provides not only a basic reference for wetland management, but also a scientific perspective for understanding the impact of environmental flow regulation on aquatic organisms. The proposed method demonstrates the important potential of evaluating the effectiveness of environmental flow regulation on aquatic organisms in wetlands.

Freshwater fishes of the Río de la Plata: current assemblage structure

Abstract Few studies have addressed the composition of fish assemblages of the freshwater Río de la Plata (RdlP) and have only been limited to species lists gathered over the last two centuries. As such inventories have never been reviewed or validated by fish sampling, the richness and structure of RdlP fish assemblage are poorly known. Hence, we conducted an exhaustive literature review and a fieldwork in six coastal points of Argentina to update the species composition and determine the hierarchical structure of the fish assemblage. From the 206 species registered in the literature, 48 were not confirmed, 13 were absent, five were taken as synonymized species, 29 were supported by literature and 107 were confirmed; one was an established exotic species, and three were a non-established exotic species. The findings reported here suggest that the fish assemblage currently comprises 141 species, including four new records. Analysis of fieldwork data in number and weight of fish captured resulted in an assemblage hierarchical structure of five dominant, 22 frequent, and 45 rare species; 16 dominant, 11 frequent, and 45 rare taxa, respectively. These results could be used as baseline to monitor, manage, and preserve neotropical fish species in their southern distribution boundary.

Long-term trends of fishery landings and target fish populations in the lower La Plata basin

Abstract The La Plata basin is the second largest basin of South America and has supported important river fisheries for more than a century. In this paper, we evaluate for the first time the historical trends of landings of 21 fish taxa and the recent population trends of 27 species of commercial fishes in the lower La Plata basin (Argentina). We compiled three kinds of data sets: Total fishery landings (between 1934 and 1986) and exports (1994‒2019), fisheries monitoring programs of Chaco and Santa Fe provinces in the Paraná River (2009‒2019), and surveys of fish populations in the Upper (Corrientes, 1993‒2020) and Middle (EBIPES, 2005‒2020) Paraná River. The analysis of the historical landings showed more species declining in the lower portion of the basin than in the upper basin. Regarding recent population trends, Pimelodus spp., Hoplias spp., Salminus brasiliensis, Luciopimelodus pati, and Ageneiosus spp. declined in more than one region, while Megaleporinus spp., Pterodoras granulosus, and Oxydoras kneri showed stable to positive trends, with the other species varying in their trends between regions. These tendencies could be associated to a combination of factors such as overfishing and environmental changes that would require an ecosystem approach for their adequate management.

Population responses of common carp Cyprinus carpio to floods and droughts in the Pampean wetlands of South America

Common carp (Cyprinuscarpio) is a global invader that exhibits a wide distribution in Argentina, particularly in shallow lakes and wetlands of the Pampean region. The hydrological conditions of these environments are driven by variations in annual precipitation that determine inter annual changes in water levels leading to flood-drought cycles. The present study focused on understanding the C.carpio population responses to annual rainfall regime and long-term flood and drought events in the Ajó wetlands located in the east of the Pampean region. The results of a two-year biological sampling program showed that C.carpio feeding rate, reproduction, condition, and recruitment were associated with the hydrological cycle. Otolith derived age structure of the population and back-calculated recruitment strength revealed that extraordinary flooding events generated strong cohorts while dry years resulted in low recruitment. Its long-life span (maximum 14 years in Ajó) coupled with a high fecundity, and broad diet allows C.carpio to persist in refugia during dry years and capitalize on wet years when inundation of the floodplain enhances recruitment and facilitates spread. Management and control strategies for this invader should therefore incorporate hydrological variability by promoting intensive removal campaigns during dry years when populations are dominated by large fish confined in remnant water-bodies and, during wet years, carp harvest fisheries should be promoted to reduce population density when increased connectivity is likely to facilitate spread.

Global patterns and clines in the growth of common carp Cyprinus carpio

This review provides a meta-analytical assessment of the global patterns and clines in the growth of Cyprinus carpio as measured by length-at-age (L_t ) or von Bertalanffy growth function (VBGF) parameters, mass-length relationship (W-L_t ) and condition factor, based on literature data. In total, 284 studies were retrieved spanning 91 years of research and carried out on 381 waterbodies-locations in 50 countries in all five continents. Although native C. carpio achieved larger (asymptotic) size relative to its non-native counterpart, the latter grew faster during the first 7 years of life. Lentic populations (especially in natural lakes) also achieved larger sizes relative to lotic ones and the same was true for populations in cold and temperate v. arid climates. Unlike previous studies (on much more restricted datasets), only weak latitudinal clines in instantaneous growth rate, L_t at age 3 and mortality were observed globally and this was probably due to the presence of counter-gradient growth variation at all representative age classes (i.e. 1-10 years). Slightly negative allometry was revealed by the W-L_t and the related form factor tended to distinguish the more elongated and torpedo-shaped body typical of the wild form from the deeper body of feral-domesticated C. carpio. Existing population dynamics models for C. carpio will benefit from the comprehensive range of waterbody type × climate class-specific VBGF parameters provided in the present study; whereas, more studies are needed on the species' growth in tropical regions and to unravel the possibility of confounding effects on age estimation due to both historical and methodological reasons.