Identifying major events in two sturgeons' life using pectoral fin spine ring structure: exploring the use of a non-destructive method.

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.

The sagittal otolith morphology observations of sturgeon species in Iranian waters of the Caspian Sea / Observaciones sobre la morfologia de otolitos sagitales de varias especies de esturion en las aguas iranies del Mar Caspio

The morphology of the sagittal otolith of Great sturgeon (Huso huso), Persian sturgeon (Acipenser persicus) and starry sturgeon (Acipenser stellatus) species from the Iranian waters of the Caspian Sea were studied. Three otolith measurements and three shape indices were recorded from 90 sturgeon specimens. Fish biometry traits were measured and relationship between sagittal otolith length (OL)-total length (TL), and sagittal otolith weight (WO)-body weight of fish (BW) were estimated. Sagittal otolith has a triangle shape with irregular edges in great sturgeon, elongate triangle with smooth surfaces in Persian sturgeon, and relatively circular with smooth surface in starry sturgeon. The ratio of the WO/BW in starry sturgeon was significantly higher ( P <0.05) than great sturgeon and Persian sturgeon. There is a direct proportional relationship between BW and WO in Persian sturgeon (r2=0.7), great sturgeon (r2=0.9) and starry sturgeon (r2=0.9). Regression line slope for these relationships in starry sturgeon were less than Persian sturgeon and great sturgeon. Furtheremore, there is significant linear regression between OL-TL. Results showed that it is possible to identify Caspian sturgeon species based on body morphometry and sagittal otolith characteristics.

Se estudió la morfología del otolito sagital del gran esturión (Huso huso), el esturión persa (Acipenser persicus) y el esturión estrellado (Acipenser stellatus) de las aguas iraníes del Mar Caspio. Se registraron tres mediciones de otolitos y tres índices de forma, de 90 especímenes de esturión. Se midieron los rasgos de la biometría de los peces y se estimó la relación entre la longitud del otolito sagital (LO) - longitud total (LT) y el peso del otolito (PO) - peso del cuerpo de los peces (PC). El otolito sagital tiene forma de triángulo con márgenes irregulares en el gran estu- rión (Huso huso), triángulo alargado con superficies lisas en estu- rión persa y relativamente circular con superficie lisa en esturión estrellado. La relación del PO / PC en el esturión estrellado fue significativamente mayor (P <0.05) que el gran esturión y el estu- rión persa. Existe una relación directamente proporcional entre PC y PO en el esturión persa (r2 = 0.7), el gran esturión (r2 = 0.9) y el esturión estrellado (r2 = 0.9). La pendiente de la línea de regresión para estas relaciones en el esturión estrellado fue menor que el esturión persa y el gran esturión. Por otra parte, existe una regresión lineal significativa entre LO-LT. Los resultados mostraron que es posible identificar especies de esturión del Caspio basadas en la morfometría corporal y las características del otolito sagital.