Biological Parameters and Fisheries Indices of Beluga Sturgeon Huso Huso in the Southern Caspian Sea

Abstract

There is a significant lack of data for the biological parameters of beluga or great sturgeon, the largest fish in the Caspian Sea. The age, growth and fisheries indices for the stock status of beluga was investigated in the south Caspian Basin of Iran between 1990 and 2011. Fork lengths ranged between 113-420 cm and weights from 8.0 to 725.0 kg. The growth parameters were L∞ = 440 cm, K = 0.027 year−1, t0 = − 5.8 years. The age at first capture (tc) was 13.1 years. The long-term age composition data showed age up to 63 years, and the ages 12-19 years comprised 76.7% of the total catch. The generation length was 33 years. The values of “KF” were close to 1 or >1, indicating that beluga sturgeon is in a favorable condition in the southern Caspian Sea. The length distribution showed that 24.2% of the catch is comprised of juveniles. Based on the age structure and age at first maturity, recruitment and growth overfishing occurred in beluga stocks. Therefore, increased length or age at first capture in future fishery policies should be implemented. The mega-spawners represented 4.4% of the fish captured and revealed an unhealthy population structure.

Demographics of great sturgeon (Huso huso) in Iranian waters of the Caspian Sea (2008–2010)

“…The mean weight of the great sturgeon determined in this study was lower compared to that found in the periods from 1990 to 1994 (Taghavi-Motlagh 2001) and from 1990 to 2011 (Fazli et al 2020), and with larger mature individuals which enter the Volga River (Ruban & Khodorevskaya 2011). In general, it was found that females had a greater fork length and body weight compared to males.…”

“…Only the oldest fish showed multiple vascular channels and compressed or abnormal bands in the margin of the anterior fin spine, which made fin cross sections. The mean fork length of both sexes revealed a decrease in size compared to data for great sturgeon from 1990(Taghavi-Motlagh 2001 and from 1990-2011 (Fazli et al 2020), and also the mean fork length of both females and males was lower than that reported by Ruban & Khodorevskaya (2011) for great sturgeon from the Volga. These differences may be related to the capture of predominantly mature migrating fish in this area, while the catches in the southern part contained both mature and immature fish (Taghavi-Motlagh 2001;Ghadirnejad et al 2010).…”

“…The maximum age determined for this species in 1940 ranged from 107 to 118 years (Babushkin & Borzenko 1952). It was later estimated at 50 to 63 years (Kosarev & Yablonskaya 1994;Fazli et al 2020) but our study indicated that the maximum age is 25 to 30 years. The presence of females in older classes (Pirogoviskiy & Fadeyeva 1982) may represent a life strategy that gives them a longer life expectancy (Roff 1984).…”

“…Pleuronectes platessa L. (Rijnsdorp, 1989), Gadus morhua (Olsen et al 2005) and Micropterus dolomieu (Dunlop et al 2005). The mortality coefficient of female great sturgeon in 1990(Taghavi-Motlagh 2001) and 1990(Fazli et al 2020) was lower than that obtained in this study for females and males. This indicates that intensive commercial fishing may be a causative factor in the sharp decline of the great sturgeon stock, the increase in the annual mortality rate and the decrease in the survival rate.…”

Spatial and temporal trends in the relative abundance of Caspian sturgeon during 2006–2022

“…Bycatch of juvenile and young A. persicus sharply increased on the eastern coasts of the Caspian Sea from 2000 to 2004, and was expected to increase into the 2010s with effective regulation in the whole Caspian Sea (Moghim et al (2006). However, stocks of all five species declined sharply and were critically endangered (Fazli et al, 2020(Fazli et al, , 2021Fazli, Kaymaram, & Daryanabard, 2022;Khodorevskaya et al, 2014;Ruban & Khodorevskaya, 2011;Tavakoli et al, 2019). In the present study, a bycatch of juvenile and young sturgeon since 2006 was used to assess the status of these species' populations.…”