No abstract

The gobioid fish Apocryptes bato (Hamilton, 1822) is a species of mudskipper found in Bangladesh, India, and Myanmar. The reproductive biology of A. bato including sex ratio, size at sexual maturity, breeding season, fecundity, and condition factor was studied in the Payra River, southern Bangladesh during May 2016 to April 2017. A total of 1,028 specimens (303 males and 725 females) were collected. The overall sex ratio was significantly different from the expected value of 1:1 (male: female = 1:2.39, χ2 = 173.23, p < 0.05). Size at sexual maturity was estimated as 4.9 cm standard length. Monthly variations in gonadosomatic index indicate that the main breeding season is from May to December. There was a significant positive correlation of body length and body weight with fecundity. Fulton's condition factor varied in both sexes and was attributed to variations in GSI with maturity. Breeding season was significantly associated with rainfall, but not air temperature. Our findings should improve management and conservation of this fish in the Payra River and surrounding ecosystems.

The present study describes the length-weight (LWR) relationship, length-length (LLR) relationship, and condition factor (K) of four small indigenous fish species from the Payra River, southern Bangladesh, namely Mastacembelus pancalus, Lepidocephalus guntea, Salmostoma bacaila and Mystus vittatus. A total of 867 specimens, representing 4 species of 4 families used for this study were caught by traditional fishing gear from July to October 2018.Standard length (SL) and total length (TL) for each specimen were measured by digital slide calipers and each body weight (BW) was taken by a digital balance. The allometric coefficient b of the LWR was close to the isometric value (b=3.078 and 3.028) in M. pancalus and L. guntea respectively, although it suggested negative allometric growth in M. vittatus (b < 3.00), whilst positive allometric growth in S. bacaila (b > 3.00). All the LWRs were highly significant (P < 0.05) and most of the coefficients of determination values were ≥ 0.857. The results further indicated that the LLRs were highly correlated (r 2 ≥ 0.939; P < 0.05). Fulton's condition factor (K) by month basis ranged from 0.52 (in M. pancalus) through 1.89 (in M. vittatus). The results of this study can be very effective for stock assessment of this four species in Payra River as well as in the surrounding ecosystems.