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- ArticleAçık Erişim2026Assessment of Population Parameters for Fisheries Management in a Pressured Ecosystem: A Case Study of Sapanca Lake (Türkiye)
Şen Özdemir, Nurgül; Aydın, Erdinç; Sökmen, Teoman Özgür
Sapanca Lake is a tectonic freshwater lake ecosystem whose water balance and ecological integrity are increasingly threatened by urbanization, pollution, climate change, and declining water levels. To assess recent changes in the fish community, length–weight relationships (LWRs), condition factors (CFs), sex ratios (F/M), and standing stock biomass estimates were determined for eight fish species (Blicca bjoerkna, Scardinius erythrophthalmus, Carassius gibelio, Esox lucius, Silurus glanis, Perca fluviatilis, Abramis brama and Cyprinus carpio) sampled between December 2024 and April 2025. According to standing stock biomass assessments, Cyprinus carpio showed the highest biomass (297.67 tons), while Abramis brama had the lowest (22.72 tons). Most species showed positive allometric growth (b > 3), suggesting generally favorable feeding conditions. In contrast, the main predatory species, E. lucius (b = 2.89) and Silurus glanis (b = 0.21), exhibited negative allometric growth, likely due to limitations in food availability and prey abundance. The CF values were generally >1, indicating good physiological status; however, lower CF values in A. brama (1.18) and B. bjoerkna (1.19) suggest species-specific ecological limitations. Sex ratio analysis revealed pronounced female dominance across species, ranging from complete female dominance (F/M = 1/0) in Carassius gibelio to a female-biased ratio of 1/0.04 in Scardinius erythrophthalmus, likely driven by seasonal sampling effects, sex-specific behavior, and species-specific reproductive strategies. Overall, the results indicate increasing trophic imbalance and ecological stress in Sapanca Lake, emphasizing the need for standing stock biomass assessments and ecosystem-focused fisheries management in tectonic lakes under hydrological pressure.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Length-weight Relationships and Condition Factors of Çaltıcak (Taşkısığı) Lake (Sakarya, Türkiye) Fish Species
Şen Özdemir, Nurgül; Aydın, Erdinç; Sokmen, Teoman Ozgur
Length-weight relationships (LWRs) and Fulton condition factor (CF) of 8 fish species belonging to different families (Bilicca bjoerkna, Scardinus erythrophthalmus and Carassius gibelio from Cyprinidae, Esox lucius from Esocidae, Silurus glanis from Siluridae, Perca fuliviatilis from Percidae, Abramis brama from Leuciscidae) obtained from commercial fishermen in Çaltıcak (Taşkısığı) Lake (Sakarya/Türkiye) were examined. LWRs and CF of the fish species were analyzed between March 2021 and March 2022. C. gibelio and E. lucius show positive allometric growth, B. bjoerkna,S. glanis and P. fuliviatilis and A. brama showed negative allometric growth, while S. erythrophthalmus and T. tinca show isometric growth. The lowest CF values of the fish species were also determined in S. glanis (0.62) and E. lucius (0.69). It is thought that the information obtained in the study about the LWRs and CF values of the fish species in Çaltıcak Lake will be beneficial for commercial fishing and fisheries management in the region.
RDL Kalıcı Kaydıİncele