Assessment of Stocking Activities on the Native Brown Trout Populations from Nestos River (Southern Balkans) Inferred by mtDNA RFLP and Sequencing Analyses

Alien fish introductions, conducted towards the ichthyofauna enhancement in local drainages, have been occasionally proved harmful for the indigenous freshwater fish populations. The present study was designed to assess the impact of stocking activities, carried out in the past decades with fingerlings originating from Acheloos river hatcheries, on the native trout (Salmo sp.) populations of Nestos River, Greece. Trout specimens collected from several tributaries of Nestos River and were analyzed by means of PCR-RFLP and sequencing targeting the mitochondrial ND5-ND6 genes and the entire control region, respectively. It should be mentioned that trouts from Acheloos mainly belong to the marmoratus mitochondrial DNA (mtDNA) lineage, while the autochthonous trouts from Nestos belong to the Adriatic lineage. Both methodologies demonstrated that most samples from the three tributaries located at the lower part of Nestos constitute offspring of the fingerlings transferred from Acheloos hatcheries. Therefore, these tributaries have been strongly affected by stocking activities with a potential complete loss of their autochthonous trout. On the other hand, it seems that trout populations from higher altitude tributaries have not been affected by stockings. Hence, efforts should be undertaken in order to prevent the prevalence of the non-indigenous translocated Salmo in higher altitude tributaries, in conjunction with a management plan designed for the total trout populations from the area, speaking of which it has been recently included to the National Park of Rodopi Mountains.

Management of alien aquatic invasive species: Strategic guidelines and policy in India

The present article is aimed at understanding current policies and implementation strategies for the management of aquatic invasive species in India and identifying opportunities for improvement. Existing management approaches and policies have briefly been put into place concerning fish introductions and aquatic invasive species, but looking at their effectiveness, it is argued that mitigating the negative impacts caused by invasive species should be at the core for their successful management. International institutions have explicitly recognized the need to contain and eradicate biological invasions and have set of relevant guidelines and enforcements. In India, risk assessment, risk management, quarantine, biosecurity and regulatory mechanisms have been developed and implemented to filter fish introductions and consequently check aquatic invasions. Nevertheless, invasive species introduced into the inland waters are emerging as ‘chronic risks’ to the aquatic biodiversity and ecosystem services. It is imperative that these emerging issues are put on the National Agenda and Action Plan to regulate fish invasions and minimise their adverse impacts. A National Policy on prevention and control of aquatic invasive species is urgently needed to deal with nuisance and harmful impacts. Some future needs have also been suggested to tackle this issue.

Aquarium trade and fish farms as a source of non-native freshwater fish introductions in French Guiana

Rivers of French Guiana are still little invaded by non-native fish, but several fish introductions were recently recorded through the development of aquarium fish trade and fish farms. Here we report records of 11 non-native fish species. Among them, four (Cichla monoculus, Heros efasciatus, Mesonauta guyanae and Poecilia reticulata) are established and one of them (Heros efasciatus) is rapidly increasing its spatial range. Two species (Hyphessobrycon eques and Pterophyllum scalare) were not retrieved in recent records and are probably extinct from French Guiana. The establishment status of the five other species (Arapaima gigas, Colossoma macropomum, Cyprinus carpio, Oreochromis mossambicus and Osteoglossum bicirrhosum) is uncertain and only a few specimens were observed in the wild. Nevertheless, these species, intensively reared in nearby countries, belong to highly invasive species able to cause detrimental impacts on recipient ecosystems. Those first occurrences of invasive fish species in French Guiana should therefore act as an early warning for both researchers and environmental managers.

Using social and physical variables to assess vulnerability of northwestern Montana lakes to illegal fish introductions

The spread of non-native fish species is a common problem in lakes and streams worldwide. Species that establish viable populations in a new environment can seriously deplete populations of native species and desired sportfishes. In some instances, extirpation of a native species has occurred. In western North America, the most common avenue by which non-native species invade new waterbodies is illegal stocking by anglers, aquaculturists, and others. Thus, preventing further illegal fish introductions is of the utmost importance for native aquatic species. Using data collected by state agency personnel from 1953 to 2015, we examined multiple social and physical variables to determine the factors that best explain which lakes in northwestern Montana had past illegal fish introductions. An equation using elevation, surrounding population, and fishing pressure was found to best fit the data. This equation was then used to calculate an index of the vulnerability of lakes within the region to future illegal fish introductions. The techniques used in this study have broad applicability that can be used in many regions with illegal fish introductions, and ultimately help to alleviate the problem.

First record of the Guppy (Poecilia reticulata Peters, 1859) in inlandwaters of Turkey

The ever-increasing global trade of ornamental aquarium fishes is one of the most important pathways for aquatic invasion. Occurrence of ornamental freshwater fishes in natural freshwaters has been increasing in recent years. The ornamental trade accounts for a limited but steadily growing proportion of fish introductions to Turkish inlandwaters. In this study, Guppy, Peocilia reticulata, is recorded for the first time from natural inlandwaters of Turkey. P. reticulata was probably released into the wild, but is now established in aquifer of Çeşme-Ildır (İzmir).

Moving repatriation efforts forward for imperilled Canadian freshwater fishes

Freshwater ecosystems are among the most threatened environments on our planet. Disturbances across the terrestrial landscape accrue within freshwater ecosystems and, combined with global stressors such as climate change and invasive species, create a complex situation for recovering imperilled fishes. Given the drastic global decline of freshwater fishes, similarly extreme efforts are needed for their conservation and recovery — repatriation represents one such opportunity. Species repatriation describes the act of releasing a species in areas where extirpation has occurred. Paradoxically, a long history of fish introductions for recreational purposes exists, yet examples of repatriation for imperilled fishes are relatively rare compared with terrestrial species. Stemming from the restoration and species introduction literature, we identify five ecological themes to consider when evaluating repatriation potential of freshwater fishes and suggest that repatriation represents the “drastic” approach needed to achieve meaningful conservation milestones.