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Age frequency distribution for females (n = 23) and males (n = 46) of Sepia bertheloti caught off Morocco
Source publication
In this study, we explored the feasibility of using the beaks of the African cuttlefish Sepia bertheloti for age estimation and growth analysis. The rostrum sagittal section (RSS) of the lower beak was the most suitable region in the species. It was applied in samples caught off Morocco and Guinea-Bissau between June 2018 and January 2020. A maximu...
Citations
... Focusing on age, a preliminary study conducted in the Central-East Atlantic showed that beaks could be a promising tool for age estimation in Sepia officinalis using the rostral section because the visibility of increments was better than that of lateral walls in the whole known-age sample (from 1 to 175 days old) [28]. Another recent study in the same geographical area on S. bertheloti selected the rostrum section because it showed the clearest pattern of growth increments [37]. Our study on beaks returned a good outcome given the perfect visualization of the growth increments along the lateral wall. ...
Simple Summary
Determining the age of cephalopods is essential for understanding their life history, which is in turn crucial for assessment and management. The short lifespan with a single reproductive event, high natural mortality rates, and rapid growth in these species make the application of traditional age-based models impractical. Most hard structures of cephalopods, such as mandible (beaks) and statoliths, can store ontogenetic events through the formation of periodic marks or growth increments. Statoliths are paired calcareous structures located in two anterior chambers of the head. In this work, for the first time in the Mediterranean, we successfully performed age estimation in wild cuttlefish Sepia officinalis using beaks and statoliths. Based on daily increments that were previously validated in statoliths, the beaks were cross-verified. As the beak presented more advantages in age studies than statoliths, due to the relative simplicity of its processing method, it was eventually proposed as a suitable hard structure to study the age of S. officinalis.
Abstract
Establishing the age of cephalopods is crucial for understanding their life history, which can then be used for assessment and management. This is particularly true for the common cuttlefish Sepia officinalis (Linnaeus, 1758), one of the most important resources for coastal fisheries. For this reason, an age analysis of S. officinalis was performed for the first time in the Mediterranean, using beaks and statoliths from 158 wild specimens (55–222 mm mantle length; 23–1382 g total weight) at different maturity stages (immature to mature). Growth increments were counted in the lateral wall of the upper beaks and the lateral dome of statoliths. In both cases, a good relationship was found between the counts and the sizes of the animals. The low values of coefficients of variation between the readings obtained for beaks (3.96 ± 1.87%) and statoliths (4.00 ± 1.89%) showed a high level of precision and accuracy in the readings. However, the analysis was simpler for beaks, which were all successfully analyzed, while it was more complex for statoliths, with 69% being lost due to rejection or overgrinding. Based on daily increments previously validated in statoliths, the beaks were cross-verified by comparing their counts with those from statoliths extracted from the same 83 specimens, obtaining a statistically significant relationship between the two counts, confirmed by the ANOVA test. Absolute growth rates that were assessed using both beaks and statoliths indicated that the two sexes had a higher growth rate at 122 and 182 days, which subsequently declined in older specimens. Due to the relative simplicity of its processing method, the beak was finally proposed as a suitable hard structure to study the age of S. officinalis. We also confirmed the good readability of increments in the lateral wall of the beak, which could be considered a valid alternative to the rostrum surface.
Cuttlefish (Sepia spp.) is one of Indonesia's fisheries resources with high economic value. It is often caught in the northern Java waters, including Lamongan. As it is high value, cuttlefish resources should be managed to ensure sustainability. However, information on its biology and population dynamics is limited as the basis of fisheries management. This research aimed to identify species of cuttlefish and to estimate its biological aspects and population dynamics. Samples were randomly collected at Brondong Fishing Port from July to September 2022. The result indicated that there were two species of cuttlefish, Sepia aculeata (needle cuttlefish) and Sepia pharaonis (pharaoh cuttlefish), with a proportion of 57.1 and 42.9%, respectively. In addition, S. pharaonis was bigger and heavier than S. aculeata. The mean mantle length = 10.5 cm and weight = 166.6 g for S. aculeata, while S. pharaonis has mean mantle length = 11.4 cm and weight = 208.1 g, and both species have negative allometric growth patterns. Moreover, the asymptotic mantle length (L∞) = 24.6 cm and 22.7 cm, growth rate (K) = 0.68 year-1 and 0.78 year-1 , total mortality rate (Z) = 1.96 year-1 and 4.61 year-1 , natural mortality rate (M) = 0.97 year-1 and 1.64 year-1 , fishing mortality (F) = 0.99 year-1 and 2.97 year-1 , and exploitation rate (E) = 0.51 year-1 and 0.65 year-1 for S. aculeta and S. pharaonis respectively. This finding might contribute to managing cuttlefish fishery in the north Java waters, especially in East Java.
The external morphology and morphological variations of Sepiella inermis vary across regions, necessitating investigation. However, the histological information on the subcutaneous gland has been insufficient to describe it. In this study, specimens were systematically collected and characterized from the Gulf of Thailand. Regarding external morphology, female cuttlebones exhibit greater width and more pronounced curves compared to males, while males feature 17–19 white dots along the fin margins. The presence of the subcutaneous gland was discerned during the embryonic stage at stage 19. A histological study of the subcutaneous gland illustrated the structure and development of the gland in both embryonic and adult stages, with four layers of membranes covering the gland. In the adult stage, trabeculae are dispersed throughout the gland, whereas in the embryonic stage, they form four distinct lines. The morphometric analysis revealed significant differences between males and females (p < 0.05) and morphological variations among the seven locality groups within the sexes were observed (p < 0.05) in Chonburi Province. According to the discriminant analysis results, there were significant differences (p < 0.05) between the groups in Surat Thani Province. Examining the length–weight relationship between dorsal mantle length and body weight showed significant differences between the sexes, indicating an allometric growth.
