Notes on the Summer Life History Traits of the Non-Native Pumpkinseed (Lepomis gibbosus) (Linnaeus, 1758) in a High-Altitude Artificial Lake

In the present study, the biology of the pumpkinseed Lepomis gibbosus in the artificial lake of Aoos, located in northwestern Greece, was investigated. The samplings of the pumpkinseed were conducted from the shore using a portable electrofishing device over a 4-month period (July 2021–October 2021). A total of 581 specimens were caught, with an average length of 62 mm. The sex ratio of female to male was estimated to be 1.0:1.7, and the percentage of mature specimens was estimated for all of the months to be above 52%, matching the highest percentage in July (57.4%). The b value of the length–weight relationship ranged from 3.16 in September to 3.31 in July. The value of the L∞ and K was estimated to be equal to 119 mm and 0.36 years−1, respectively, and the value of φ′ was equal to 3.707. The total mortality was estimated to be equal to 1.63 ± 0.48 y−1 (R2 = 0.96), and the natural and fishing mortalities were 0.83 and 0.80, respectively. The maximum age was 6 years, and the theoretical maximum age was 8 years. In the current study, the value of the L∞ was estimated to be near the European average but significantly lower than the North American one, whereas the value of the K was slightly higher than the European average. The small size of the specimens obtained in Aoos Springs was most likely owed to the combined impact of the investigated lake’s high altitude and low food availability, resulting in a limited factor for species expansion.