Age, growth, reproductive biology and mortality of Cranoglanis multiradiatus , a threatened freshwater fish in Hainan Island, China

Abstract

Life history traits like age, growth, reproduction and mortality are principal factors in fish research and management (Mgaya & Mahongo, 2017). Fish age is an important biological variable, which is essential for calculating growth parameter and mortality (Campana, 2001). The knowledge of reproductive characteristics is important for understanding the population dynamics. For example, the estimated age and size at 50% maturity of the fish provides information about the critical size that can be harvested (Cope & Punt, 2009).Additionally, the knowledge of seasonal spawning time can ensure the time, when the fish is vulnerable to overharvest and requires the fisherman to stop fishing until spawning is finished (Adams et al., 2018). However, the information of life history is limited for some threatened and endemic freshwater fishes in Hainan Island (Cao et al., 2016;Xiong et al., 2018). Cranoglanismultiradiatus belongs to Siluriformes, Cranoglanididae, Cranoglanis, which is endemic to Hainan Island

Age, growth, maturity and mortality of the tapetail anchovy Coilia brachygnathus (Engraulidae) in Lake Honghu, China

“…Annuli in C. brachygnathus otoliths and scales are laid down in April and May. Hence, to fit the von Bertalanffy growth model, each fish was assigned a more precise age by fixing its birth date as June first, the peak breeding activities coincided with flooding season, and considering the date of capture (He et al ., 2008; Liu et al ., 2021). The age of the fish was equal to the number of annuli rings plus the number of days from the nominated birthdate to capture, therefore it was calculated based on the following equation (He et al ., 2008; Stewart & Hughes, 2007): , where A is age in years, N is the number of opaque annuli rings countered and Dc is the number of days from the nominated birthdate to capture.…”

“…Hence, to fit the von Bertalanffy growth model, each fish was assigned a more precise age by fixing its birth date as June first, the peak breeding activities coincided with flooding season, and considering the date of capture (He et al, 2008;Liu et al, 2021). The age of the fish was equal to the number of annuli rings plus the number of days from the nominated birthdate to capture, therefore it was calculated based on the following equation (He et al, 2008;Stewart & Hughes, 2007)…”

Age, growth, reproduction and status of resource development of Ptychidio jordani, a critically endangered freshwater fish in the Hongshui River, China

“…Moreover, the t ‐test was used to analyse whether the body length of females and males had significant differences and to test the significance of the b value in the relationship between body length and weight. χ 2 was used to test whether the ratio of male to female was significantly different from 1:1 (Liu et al ., 2022).…”

“…All mature ovaries were preserved in a 5% neutralized formaldehyde solution for calculating fecundity. Taking the anterior, middle and posterior of the ovary from both sides as an ovarian sample (Liu et al ., 2022), absolute fecundity ( AF ) was calculated as AF = nG / g , where AF was the total number of eggs in the ovary, n was the number of eggs in sub‐sample, G was the mass of the whole gonads and g was the weight of sub‐sample (Liu et al ., 2022). Relative fecundity ( RF ) was obtained by dividing the AF with M E .…”