Population Structures and Diets of Two Species of Pisodonophis (Ophichthidae) from the Southwest Coast of Taiwan

Abstract

This study was used to lift nets and trap net fishing at intertidal zone of lagoon and estuarine regions of southern Taiwan. From July 2013 to July 2018, a total 420 specimens of Pisodonophis were analyzed, the average total body length (TL) and average body weight (W) of P. boro eels are 68.4 ± 11.9 cm and 140.4 ± 86.1 g (N = 194), respectively. Typically, P. cancrivorus eels are smaller (TL = 52.8 ± 9.2 cm) and lighter (W = 107.9 ± 73.7 g [N = 119]) than P. boro eels. The natural logarithmic linear relationships between the TL and W of P. boro and P. cancrivorus are respectively expressed as ln(W)b = 2.4405 ln(TL) − 5.4448 (R2 = 0.796, N = 194) and ln(W)c = 3.2168 ln(TL) − 8.2027, (R2 = 0.934, N= 119). P. cancrivorus typically preys on shrimp, crab, and fish; lab assessment revealed that the frequencies of occurrence of these foods in their guts were 49%, 21%, and 15%, respectively (N = 100). The main catch months of P. boro were during the rainy season, and that of P. cancrivorus were the winter season in Taiwan. The average W values of P. boro from Jhuoshuei and Puzih estuaries were 343.2 ± 218.8 g (N = 91) and 140.4 ± 86.1 g (N = 194), respectively. Furthermore, the results of the study revealed that the Puzih estuary is overfished. We suggest that fishery management units should develop some protection measures for the conservation of aquatic ecosystems in estuarine regions. For example, the P. boro weighing less than 113 g will be released back to the estuary.