Population Structure and Relative Growth of the Marbled Crab ( Pachygrapsus marmoratus ) in the Aegean Sea (Turkey)
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Population Structure and Relative Growth of the Marbled Crab (Pachygrapsus marmoratus) in the Aegean Sea (Turkey) Fikret Öndes 1
&
Onur Karadal 1
Received: 5 March 2020 / Revised: 18 June 2020 / Accepted: 22 June 2020 # Springer Nature Switzerland AG 2020
Abstract Although crab Pachygrapsus marmoratus, is one of the common species in the intertidal zones of the Aegean coasts of Turkey, its’ population structure has not been investigated to date. This study aimed to provide information on population characteristics of Pachygrapsus marmoratus, including the sex ratio, size distribution, spawning period, relative growth and catch per unit effort (CPUE). The samples were collected by hand monthly between January 2018 and December 2018, from the rocky shores of Izmir, Turkey. The results indicated that males were dominant except for the months of July, August and September. The CW (carapace width) of female and male crabs ranged from 5.5 to 36.0 mm and 5.5 to 40.0 mm, respectively. The berried (eggcarrying) females were found in May, June and July and their CW varied from 13.0 to 27.0 mm. Only 0.8% of the P. marmoratus population was shown to be infected with the parasite Sacculina sp. The CPUE of P. marmoratus significantly changed monthly and there was a significant correlation between the CPUE and seawater temperature. Concerning the relative growth, the carapace width-cheliped length relationship in males and carapace width-abdomen width relationship in females showed positive allometry. Males were significantly heavier in comparison to females of the same size. Future survey designs would need to investigate whether spatial differences in the population characteristics and size at maturity occur in the Aegean coasts of Turkey. Keywords Pachygrapsus marmoratus . Ecology . Catch per unit effort . Allometry . Eastern Mediterranean
Introduction Rocky shores support ecological functions including nursery provision, spawning area, migration, and reproductive areas (Seitz et al. 2014). In addition to their ecological importance, rocky shores provide many opportunities to humans including leisure, relaxation, and their fauna and flora members are used for food, bait and ornamental aims. However, as in other parts of the world, the intertidal ecosystems of the Mediterranean have been threatened for the last several decades by increased human activities, such as poaching, habitat destruction, pollution, and global warming (Milanese et al. 2011; Marchini et al. 2019). Thus, it is important to protect and monitor the fauna and flora of these ecosystems. One of the important inhabitants of intertidal areas are grapsid crabs, which generally exhibit high abundance and intense activity. They also influence the sessile community owing to the foraging activities * Fikret Öndes [email protected] 1
Faculty of Fisheries, Izmir Katip Çelebi University, 35620 Izmir, Çiğli, Turkey
and contribute to the energetic flow, because they are also consumed by some vertebrate species such as gulls (Flores and Paula 2002a). The main
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