Abstract:Sierra Leone is located on the west coast of Africa, and owing to its unique geographical location and climate, it has relatively suitable hydrological conditions on the continental shelf for providing ideal habitats and breeding grounds for many fish species. The fisheries play a crucial role in Sierra Leone's economy. Sphyraena guachancho is a critical economic fish and a significant protein source for coastal livestock due to its wide distribution, excellent meat quality, low price, and easy capture. This study focused on the basic biological characteristics of S. guachancho, providing a reference for further in-depth research and the rational development of fishery resources. The relationship between body length and weight is an essential aspect of fisheries biology research, and obtaining the accurate and appropriate body length and weight relationship is crucial for fisheries management. It can provide information on the size and body shape of a fish, allow the estimation of the average weight of fish of a certain length in a population, indicate the health status of a fish, allow comparison of the growth status of the same fish species in different regions, and provide vital information for fish breeding research. The sex ratio provides information on the composition of males and females in a group and indicates the dominant gender. This is the basic information necessary for understanding fish reproduction and conducting a population assessment. A model for predicting the quantity and quality of food required by fish based on feed levels and satiety provides an ecological basis for rationally utilizing aquatic feed resources, improving aquaculture efficiency, and investigating fish populations. In this study, 2,135 S. guachancho were sampled from six scientific expeditions (September, October, December, January, April, and May) from 2019 to 2021, and their basic biological characteristics, such as body length and weight composition, sex ratio, gonadal maturity, body length at initial sexual maturity, food intake level, and plumpness were studied. The results showed that the body length range of the S. guachancho was 50–845 mm with a single peak distribution. That for the advantage group was 175–345 mm, accounting for 74.52%. The weight range was 0.9–4,000.8 g, and that for the advantage group was 25–225 g, accounting for 71.33%. The relationship between the body length and weight was W=3.339×10-5L2.758, indicating negative allometry growth. The male-to-female ratio was 0.56:1, which is significantly different from 1:1. The maturation of the gonads was mainly in stages Ⅱ and Ⅲ, with a relatively small proportion of individuals in stages Ⅴ and Ⅵ. The body length of male and female individuals at initial sexual maturity was (269.982±2.340) mm and (259.846±3.397) mm, respectively. The feeding level was mainly level 0, and as the body length increased, the proportion of fish with an empty stomach gradually increased. The plumpness range was between 0.59 and 1.25, with an average value of 0.86±0.02. There were certain differences in fertility levels between different months. As the body length increased, the plumpness showed a trend of first increasing and then decreasing. The statistical analysis results showed significant differences in the body length and mass distribution between male and female populations of S. guachancho (P<0.01). The body length and mass distribution in different months differed significantly (P<0.01). The body length and body mass distribution in different seasons also had highly significant differences (P<0.01). The body length significantly affected gonadal maturity (P<0.01). Below a certain body length, there was no significant linear correlation between the month and gonadal maturity (P>0.05). The body length significantly affected the feeding intensity of S. guachancho (P<0.01), whereas the month had no significant impact on this (P>0.05). The maturity of the gonads significantly affected the level of food intake (P<0.01). The body length significantly affected the level of fullness (P<0.05), whereas the month had no significant impact on this (P>0.05).
