Effects of Fishing on the Population of Speckled Pavon Cichla temensis in the Middle Negro River (Amazonas State, Brazil): A Decrease in the Size of the Trophy Fish?

Fishing acts selectively on exploited fish stocks, catching larger individuals and altering age and size structure. Thus, the objective of this study was to evaluate the impacts of a multi-use fishery in regards to the size truncation of populations of Speckled PavonCichla temensis. Data collection was carried out in the middle Negro River region, where the two modalities of recreational and commercial fishing occur with greater intensity. Questionnaires were administered to fishers in order to collect information on fishing. Individual fish were captured by recreational fishers in different rivers, were measured and weighed, and were released back into their environments. Weight (g) and TL (mm) data were used to assess the size structure at different fishing intensities. Asymmetry measurements were performed, and kurtosis of the distribution curve of the population was assessed. Linear models were also performed for both fisheries. The analysis of length distribution, asymmetry, and kurtosis showed a trend toward a decrease in the mean length of Speckled Pavon in line with the increase in fishing intensity. In linear models, the average distance (km) between fishing grounds and the fleet headquarters showed a positive relationship only for recreational fishing, which indicates that with an increasing distance from the municipality, the possibility of catching larger individuals increases and, consequently, the fishing yield also increases. The number of fishers presented a negative relationship, indicating a decrease in mean size and mean yield with increasing numbers of fishers in both modalities. The model predicted that low exploitation would cause a decline in the abundance of trophy fish. The results suggest that the Speckled Pavon population of this region exhibits signs of high exploitation and that fisheries management measures should be implemented to ensure the sustainability of stocks and fisheries that have high socioeconomic importance in the region.