Age, growth, mortality and recruitment of thin sharpbellyToxabramis swinhonisGünther, 1873 in three shallow lakes along the middle and lower reaches of the Yangtze River basin, China

Abstract

Despite being the most dominant and widespread small fish species in the lakes along the middle and lower reaches of the Yangtze River basin, Toxabramis swinhonis has been paid little attention by fisheries scientists and little is known about its population characteristics. For this reason, we estimated age, growth, mortality and recruitment of this species based on three shallow lakes, Biandantang Lake, Shengjin Lake and Kuilei Lake (BDT, SJH and KLH, respectively) in this region. A total of 13,585 (8,818 in BDT, 2,207 in SJH and 2,560 in KLH) individuals were collected during monthly sampling from July 2016 to September 2017. The results revealed that the age structures of T. swinhonis consisted of four age groups (0+–3+), with 0+–1+ year old fish comprising more than 98% of the samples. Allometric growth patterns were displayed by fish from all sampling sites and the von Bertalanffy growth functions estimated were Lt = 173.25 (1 – e−1.20 (t + 1.09)): BDT; Lt = 162.75 (1 – e−1.20 (t + 1.08)): SJH and Lt = 215.25 (1 – e−1.20 (t + 1.12)): KLH, respectively. The rates of total mortality (Z), natural mortality (M) and fishing mortality (F) at BDT, SJH and KLH were computed as 5.82, 5.50 and 4.55 year−1; 1.89, 1.87 and 1.75 year−1; 3.93, 3.63 and 2.80 year−1, respectively. Meanwhile, growth performance indices (φ′) were 0.68 (in BDT), 0.66 (in SJH) and 0.62 (in KLH), which indicated that T. swinhonis were overfished slightly in all study areas. Area-specific recruitment patterns were similar to each other, displaying evidence of batch spawning, with major peaks in April and August, accounting for 92.21% (BDT), 88.21% (SJH) and 88.73% (KLH) of total recruitment, respectively. These results showed that brief generation-time, fast growth rate, relatively high natural mortality rate and strong reproductive capacity (r-strategies) are reasons why this species became the most dominant species in many lakes of China.

Shift towards Opportunistic Life-History of Sleeper in Response to Multi-Decadal Overfishing

“…These fisheries may also be changing because of other global environmental change factors. Global climate change is already affecting the life-history traits of diverse species [22,48], and water temperatures in the middle Yangtze Lakes are projected to increase by 0.26-0.28 • C per decade [49]. Meanwhile, eutrophication is also known to effect the life-history traits of fishes [21,50].…”

Phenotypic Divergences in Growth and Reproduction Underpin the Invasion of Suckermouth Armored Catfish Pterygoplichthys disjunctivus (Loricariidae) into Lotic and Lentic Habitats in Vietnam

“…Length distribution and length-weight relationship [31] The relationship between total length and the total weight was calculated for each site using a power regression equation:…”

Reflecting onto the population dynamics of Hydrocynus brevis from Dadin: Kowa Reservoir

“…The length frequency data was used to plot Powell-Wetherall Plot [39] which was then used to obtain the initial asymptotic length (L∞) -Which is the hypothetical length a fish will reach if it were to grow forever -and Z/K. The value of asymptotic length was then fitted into ELEFAN 1 to obtain growth coefficient (K) of Von Bertalanffy Growth Formula (VBGF) and the best growth curve for better estimation of asymptotic length.…”