Abdolmalaki, S., and Psuty, I. 2007. The effects of stock enhancement of pikeperch (Sander lucioperca) in Iranian coastal waters of the Caspian Sea. – ICES Journal of Marine Science, 64: 973–980. Annual landings of pikeperch (Sander lucioperca) in Iranian coastal waters of the Caspian Sea in the early years of its exploitation, the late 1920s and early 1930s, reached some 3000 t. However, after 1935, catches declined drastically through overfishing, declining sea level, and the destruction of spawning grounds in the Anzali Lagoon. In 1990, Iran initiated a programme of artificial culture to enhance the local stock. The aim of the programme was and still is to restore the formerly abundant population of this predatory fish and to increase the profitability of the beach-seine fisheries of fishers who had stopped deploying gillnets, which pose a threat to the valuable species of sturgeon in the Caspian. Analysis of the age composition of pikeperch catches indicates that the use of beach-seines does not prevent overfishing of young pikeperch released as fingerlings in the same calendar year in which the fishing season started. No undersized fish are discarded back into the sea, because there is market demand for even the smallest fish, and a lack of communication exists between the programme beneficiaries and the management and research units. Some 15 years after it was initiated, the effectiveness of stock enhancement at a level of 4–6million fry per year remains uncertain.

The morphological characteristics of the pectoral fin spine were compared in three species of sturgeon, the Persian sturgeon (Acipenser persicus), the Russian sturgeon (Acipenser gueldenstaedtii), and the Starry sturgeon (Acipenser stellatus), all sampled from the Caspian Sea. On the basis of morphological characters of the pectoral fin spine, 62.2% of the individuals were correctly classified into separate groups. The cluster analysis also divided the three species into two major subgroups. Acipenser persicus and A. gueldenstaedtii were grouped together, suggesting a similar evolutionary basis. Significant morphological heterogeneity in pectoral fin spine characteristics was observed among the three sturgeon species. Principal component analysis identified the largest differences were in the pectoral fin spine size and the angle between distal pectoral fin spine and the horizontal line (A°). The first and second principal components (PC1 and PC2) of all observations accounted for 64.19% and 14.33% of the total variation, respectively. The combination of all analyses showed the relevance of applying pectoral fin spine shape for interspecific distinction of the three species of sturgeons.

Maturation is one of the most important life history traits that influences on many ecological characteristics of animals. This study aimed to describe the indirect distinguish of first reproduction and habitat shift (transition from the pelagic to benthic environment), using the width of translucent and annuluses of the pectoral fin spine of two sturgeon species, Persian sturgeon, Acipenser persicus, and starry sturgeon, Acipenser stellatus. Interpretation of growth bands in pectoral fin sections was done objectively using direct reading of thin sections and image analysis. The results showed that changes in the profiles of translucent and annuluses occurred at the time of habitat shift and first reproduction. Females of both sturgeons move to the deeper waters earlier than males, which can be considered as strategy for the prolonged gonad development of female individuals. Estimated age at maturity for A. persicus (9 years for female and 7 years for male) was higher than A. stellatus (7 years for female and 6 years for male), which coincide with abrupt reduction in annuli width. Marks of habitat shift and first reproduction in the pectoral fin spine are species-specific characters and enable life history traits to be identified.

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This study aimed to describe and validate the formation of the rings in the spine of the pectoral fin and to determine the coherence of the OTC mark with the rings of three species of Caspian Sea sturgeon, the Persian sturgeon (Acipenser persicus), the Starry sturgeon (Acipenser stellatus) and Ship sturgeon (Acipenser nudiventris). Validation was achieved by comparing the total radius of the fin spine of fish of known age after one and two years of growth with the measured radius of the first and second rings in the zone. There was no overlap between the measured radius for the first year and the increase for the second. The Ship sturgeon showed the largest width of the second ring followed by the Persian sturgeon and Stellate sturgeon. The results indicate that the highest growth parameter belongs to the juvenile Ship sturgeon. This research showed that chemically marking the fin spines of juvenile Acipenseridae leads to unbiased estimates and contributes to the knowledge of the population dynamics of these species. The study found that the combination of the dial ring of the pectoral fin spine with growth validated the age estimation in juvenile sturgeon Ship, Persian, and Starry sturgeon.