AUTHOR=Vejan Alti , Patimar Rahman , Jafaryan Hojjatallah , Gholizadeh Mohammad , Adineh Hossein , Aghilinezhad Seyyed Mostafa 

TITLE=Comparative population dynamics of two sympatric Palaemon shrimps (Palaemon adspersus Rathke, 1836 and Palaemon elegans Rathke, 1836) from the Southeast Caspian Sea

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.928445

DOI=10.3389/fmars.2022.928445

ISSN=2296-7745

ABSTRACT=<p>This study provides comparative information about population dynamics for the <italic>Palaemon adspersus</italic> Rathke, 1836 and <italic>P. elegans</italic> Rathke, 1836 shrimps on the southeastern coast of the Caspian Sea. Specimens were collected on a monthly basis between April 2019 and May 2020. A total of 9,643 specimens (8,478 <italic>P. adspersus</italic> and 1,165 <italic>P. elegans</italic>) were captured and examined. The highest abundance of both shrimps was observed in autumn. The male <italic>P. elegans</italic> ranged between 16.80 and 61.99 mm in total length and the females between 16.80 and 61.99 mm. The total length for male and female <italic>P. adspersus</italic> ranged from 21.46 to 69.29 mm and 18.24 to 75.46 mm, respectively. The mean ( ± SD) total length for the males and females of <italic>P. elegans</italic> was 33.65 ± 4.12 and 40.81 ± 6.59, whereas that of <italic>P. adspersus</italic> was 48.41 ± 6.27 for males and 54.68 ± 9.90 for females. Based on the b-value of LWR, the growth type of <italic>P. adspersus</italic> is positively allometric. Likewise, the relationships of female and pooled-sexes <italic>P. elegans</italic> was positively allometric, while that of male <italic>P. elegans</italic> was negatively allometric. The estimation of the VBGF parameters resulted as Total Length<sub>∞</sub> (TL<sub>∞</sub>)=71.93 mm, K=0.72 y<sup>-1</sup>, and t<sub>0</sub>=-0.176 for males, and TL<sub>∞</sub>=78.23 mm, K=0.64 y<sup>-1</sup>, and t<sub>0</sub>=-0.194 for the females of <italic>P. adspersus</italic>, while for <italic>P. elegans</italic> as TL<sub>∞</sub>=56.13 mm, K=0.91 y<sup>-1</sup>, and t<sub>0</sub>=-0.147 for males and TL<sub>∞</sub>=65.63 mm, K=0.87 y<sup>-1</sup>, and t<sub>0</sub>=-0.148 for females. The size-frequency analysis showed that both shrimps were made up of two age groups. The recruitment pattern of the shrimps was continuous with a unimodal pulse for both males and females and showed that <italic>P. adspersus</italic> is mainly recruited during the autumn and early winter while for <italic>P. elegans</italic>, during mid-summer and early autumn. The estimated maximum age was 3.35/year for the males and 2.66/year for the females of <italic>P. adspersus</italic> and 3.78/year for the males and 3.33/year for the females of <italic>P. elegans</italic>. Therefore, in this case, <italic>P. elegans</italic> shrimp is more sensitive to death than <italic>P. adspersus</italic>. The findings point to the underlying notable differentiation of the growth of the shrimps governing the processes of population dynamics. We assume that these differences result from the contrasting life-history strategies of these two Palaemon shrimps.</p>