Kehayias G., Tzavali A., Gini M., Michopoulou E., Tsounis L. 2018. Fish predation in the proximity of purse seine fishing lights: The case of Atherina boyeri (Actinopterygii: Atheriniformes: Atherinidae) in a Greek Lake. Acta Ichthyol. Piscat. 48 (1): 51-60.Background. Purse seining with the use of light is among the most common fishing practices around the world, but there is lack of studies on the effect of light on the feeding of the target species in this kind of fishery and the possible consequences for other prey species. The presently reported investigation intended to provide indications on this issue by studying the diet of Atherina boyeri Risso, 1810, which is the target species of professional purse seine fishery, conducted using light in Lake Trichonis (Greece), and by comparing the acquired results with those of previous studies where the samples were taken without using light. Materials and methods.A seven-month (June through December 2014) purse seining fishing was conducted at night around two lamp rafts: 1) a traditional lamp raft producing white LED light and 2) an autonomous photovoltaic-battery-LED lamp raft producing green LED light. Stomach content analysis was conducted on 100 randomly selected specimens from each sample and the relative prey abundance and frequency of occurrence for each prey category was estimated. Calculations of predation pressure of A. boyeri upon the fish larvae of a goby, Economidichthys trichonis Economidis et Miller, 1990, were performed. Results. The study revealed the intense effect of light on the attraction and capture of prey species rarely found in previous studies, such as the larvae of the native and endangered fish E. trichonis, amphipods, and copepod nauplii. No significant differences were observed between the two light colours. A preference shift to larger prey with the increase of ontogenetic stage of A. boyeri was observed. Several thousands of pre-recruited E. trichonis larvae may be preyed upon each night around a single lamp especially during summer. Conclusion. Fishing with light may alter the dietary preference of the target fish species and even of the entire fish community. This may have serious consequences on the younger ontogenetic stages of other fish populations, especially when it coincides with their reproductive period. Considering the lack of similar field studies, the present results may stimulate analogous investigations on the effects of fishing lights in other marine and freshwater ecosystems worldwide.

Fishing with light is an old and common practice yielding a substantial catch volume globally. Despite the popularity of the method and the efforts to improve it, there is a lack of field studies on the effects of light on the feeding preferences of the attracted fishes. A previous report suggested that purse seine fishing lights can differentiate the feeding preferences of the approaching fishes, such as Atherina boyeri Risso, 1810 in Lake Trichonis (Greece). The presently reported study aims to verify these findings by investigating the diet of the endemic Scardinius acarnanicus Economidis, 1991. The feeding behavior of S. acarnanicus was studied from 2016 to 2019 through gut content analysis, in specimens from Lake Trichonis that came from purse seining with light and specimens caught without light. The same investigation was carried out comparatively in specimens taken by gillnets from two nearby lakes (lakes Ozeros and Amvrakia), where S. acarnanicus is present, but no fishing with light is exercised. The stomach content analysis conducted on 699 S. acarnanicus specimens revealed the intense effect of light on its diet resulting in the alteration of its feeding habits towards fish predation and especially Atherina boyeri. On the contrary, the specimens taken with the use of gillnets, from the three lakes, showed a typical omnivorous feeding behavior. The findings of the presently reported study support the assumption that the elevated concentration of fish close to fishing lights alters the feeding behavior of certain species making them predators. Considering that fishing with light is practiced worldwide, this could be of great ecological significance to the ichthyofauna not only of inland waters but also of marine areas, affecting perhaps several commercial species.

Fishing ensures necessary food for humans and is inextricably linked with the environment because coastal communities developed special fishing procedures to achieve better exploitation of the aquatic resources. Lake Trichonis, Greece’s largest natural lake, is a freshwater ecosystem in which a marine species (Atherina boyeri) has entered and dominate the ichthyofauna. This species is exploited by purse seine fishing with the use of light, and previous studies revealed that the fishing lights create a particular food chain reaction, which promotes predation among the attracted fish species, one of which is Scardinius acarnanicus that preys upon A. boyeri. The purse seine fishers typically return to the lake alive S. acarnanicus, due to its low market demand, although it is the main predator of their catch. This custom, apart from causing income losses, promotes instability in the fish populations, while eventually altered the foraging behaviour of S. acarnanicus and made it a fish-predator instead of a typical omnivorous species. Based on data from official fish landing recordings, interviews with local fishers, and responses to questionnaires completed by residents of villages around Lake Trichonis, the present study investigates how changes in the dietary habits of the lakeside communities over time have led to the low market demand for S. acarnanicus. The present findings revealed an interesting relation between the dietary preferences of the local population and their ecological consequences for the fish community of this lake. This will eventually lead to the increase in the top predator (S. acarnanicus) and an inevitable decrease in the main catch (A. boyeri), affecting not only the ecological status of the lake, but also the socioeconomic characteristics of the human populations in this area. From another perspective, the results demonstrate a paradigm of adapted evolution by a wild fish under the pressure of human activities.

No abstract

Fishing with light is an old and common practice yielding a substantial catch volume globally. Despite the popularity of the method and the efforts to improve it, there is a lack of field studies on the effects of light on the feeding preferences of the attracted fishes. A previous report suggested that purse seine fishing lights can differentiate the feeding preferences of the approaching fishes, such as Atherina boyeri Risso, 1810 in Lake Trichonis (Greece). The presently reported study aims to verify these findings by investigating the diet of the endemic Scardinius acarnanicus Economidis, 1991. The feeding behavior of S. acarnanicus was studied from 2016 to 2019 through gut content analysis, in specimens from Lake Trichonis that came from purse seining with light and specimens caught without light. The same investigation was carried out comparatively in specimens taken by gillnets from two nearby lakes (lakes Ozeros and Amvrakia), where S. acarnanicus is present, but no fishing with light is exercised. The stomach content analysis conducted on 699 S. acarnanicus specimens revealed the intense effect of light on its diet resulting in the alteration of its feeding habits towards fish predation and especially Atherina boyeri. On the contrary, the specimens taken with the use of gillnets, from the three lakes, showed a typical omnivorous feeding behavior. The findings of the presently reported study support the assumption that the elevated concentration of fish close to fishing lights alters the feeding behavior of certain species making them predators. Considering that fishing with light is practiced worldwide, this could be of great ecological significance to the ichthyofauna not only of inland waters but also of marine areas, affecting perhaps several commercial species.