Population dynamics and the risk of stock extinction of Persian sturgeon (Acipenser persicus Borodin) in the Caspian Sea

Abstract

Persian sturgeon, Acipenser persicus Borodin, has been the most significant proportion of Iranian commercial sturgeon catches in the Caspian Sea over in the last three decades. This endemic species has suffered continuous population declines from the impact of anthropogenic factors. The present study filled in information gaps on underlying population biology parameters, evaluated the population status, and determined the vulnerability risk of the stock extinction of Persian sturgeon in the south Caspian basin of Iran. Growth parameters were L∞ = 224.7 cm, K = 0.058 years−1, t0 = -3.4 years. Sexual maturity of 50% for males and females was FL = 127.2 cm and 137.5 cm, respectively. The long-term age composition data showed 35 age groups, and the ages of 14–18 years comprised 80% of the total catch. Natural mortality was 0.123 years−1, and fishing mortality ranged between 0.104 and 0.331 years −1. The total biomass trend decreased and collapsed from 6,071.3 tons in 1990–91 to 144.1 tons in 2014–15. Although >93% of the catch included maturing specimens, the Persian sturgeon stock is now critically endangered because of several anthropogenic factors.

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

“…gueldenstadtii lives mainly along the west coast and middle of southern regions, while A. nudiventris is concentrated in the Kura River region (Markarova et al, 1991) and A. stellatus is found throughout the basin, but mainly spawns in the Volga, Ural, and Terek rivers. In contrast, A. persicus is mainly found in the Iranian part of the sea and inflowing rivers, including the highest proportion of the total catch of sturgeons in Iran (Fazli et al, 2020;Moghim et al, 2006).…”

“…In contrast, A . persicus is mainly found in the Iranian part of the sea and inflowing rivers, including the highest proportion of the total catch of sturgeons in Iran (Fazli et al., 2020; Moghim et al., 2006).…”

“…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.…”

“…These fish are currently categorized as “critically endangered” (IUCN, 2022). In the 1990s and 2000s, the catch and stocks of sturgeon in the Caspian Sea greatly decreased (Fazli et al., 2020, 2021; Fazli, Kaymaram, & Daryanabard, 2022; Khodorevskaya et al., 2014; Ruban & Khodorevskaya, 2011; Tavakoli et al., 2019) due to overexploitation, illegal, unreported and unregulated (IUU) fishing, poaching, habitat destruction, decreased sea surface level (SSL), increased sea surface temperature (SST), and dissolution of the Ex‐Soviet Union in 1991. Following this decrease, the Commission of Aquatic Living Sea Resources of the Caspian Sea decided to ban fishing in 2012 to restore stocks of these fishes, which have continued until 2023.…”

“…(2006). However, stocks of all five species declined sharply and were critically endangered (Fazli et al., 2020, 2021; Fazli, 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.…”