Abstract:
Stinging Catfish, Heteropneustes fossilis (Bloch, 1794) is a precious catfish of the order Siluriformes
generally known as shinghi or shinghee in Bangladesh. This fish has significant commercial worth
because of its exceptional taste, high medicinal significance with high-quality protein, calcium and iron.
It is broadly distributed in Bangladesh, Laos, India, Pakistan, Nepal, Mayanmar, and Sri Lanka. A total
of 1170 specimens were collected monthly basis using local fishing gears from the Padma River,
Bangladesh, during January 2019 to December, 2020. Male and female specimens were identified by
gonadal observation under microscope. Individual total length (TL) and body weight (BW) were
measured by measuring board and digital balance with 0.1 cm and 0.01 g precision. The length frequency
distribution was calculated by 1.0 cm TL intervals. The length-weight relationship (LWR) was calculated
by W=a*Lb. Multiple condition factors (Fulton’s, KF; allometric, KA; Relative, KR and relative weight,
WR) were analyzed for assessing the well-being of this species in relation to eco-climatic parameters. To
estimate the size at first sexual maturity (TLm), spawning season and peak - spawning season; the GSI
(gonadosomatic index in %), MGSI (modified gonadosomatic index in %) and DI (Dobriyal index) were
considered. The von Bertalanffy growth function (VBGF) was used to determine asymptotic length (L∞),
growth coefficient (K), growth performance index (Ø') and life-span (tmax).Total mortality (Z) was
estimated through length-converted catch curve method. Natural mortality (M) was determined by
log10M = -0.0066 – 0.279log10 L∞ + 0:6543log10K + 0:0463log10T; where T indicates the mean
temperature of the habitat (28.5oC). The fishing mortality (F) was calculated by Z-M. Besides,
exploitation rate (E) was assessed as E = F/Z = F / (F + M).Recruitment rate was calculated from the
analysis of the total time series of LFDs and growth co-efficients using VBGF models. Finally, MSY
(Maximum Sustainable Yield) was determined following the formula of Gulland (1983). The fin formula
of H. fossilis is: dorsal, D. 7; pectoral, Pc.1/6-7; pelvic, Pv. 6; anal, A. 62-71; and caudal, C.17-19.The
overall sex ratio (male: female=1.00:1.15) varied statistically from the predictable ratio of 1:1 (df = 1, χ2
= 4.85, p < 0.05).The overall growth pattern was possitive allometric (b > 3.00) for both sexes. Total
length varied between 8.5-22.3 cm for males and 8.9-37.7 cm for females. The KF was found the best for
assessing the well-being of this species. Moreover, KF was found significantly related with temperature
for both male and female. The WR indicated that the habitat was in balanced state. Based on GSI, MGSI
and DI index, the Lm was documented 15.5 cm in TL. Further, the higher values of GSI, MGSI and DI
denoted that the spawning season was extended from May to August, with a peak in June. In addition,
GSI was recorded statistically correlated with water temperature.The von Bertalanffy growth function
revealed growth coefficient (K = 0.42 year-1), growth performance index (Ø' = 2.84) and life-span (tmax =
4.41year). Further, H. fossilis grew swiftly with an asymptotic length (L∞) of 40.85 cm. We obtained the
natural mortality, M =0.93 year-1 is lower than the fishing mortality, F = 1.07 year-1. Therefore, with the
current fishing approach, the standing population is not quite sustainable. In addition, the maximum
permissible exploitation rate (Emax = 0.450) was less than the calculated exploitation rate (E=0.540).
Consequently, overfishing is the major significant risk for the natural stock of H. fossilis in the Padma
River of Bangladesh. During the sampling period, the recruitment pattern was more or less continuous
with two major peaks (April and August). Lastly, the MSY of H. fossilis was determined as 461.08
metric tons. The results will be very effective and helpful to establish proper fishing policy in the Padma
River.
Description:
This Thesis is Submitted to the Institute of Environmental Science (IES) , University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD)