Life-history Parameters of Shield-Head Catfish Synodontis Schall (Bloch and Schneider, 1801) in the Nile River, Egypt

Sahar Fahmy Mehanna

doi:10.32861/jac.82.87.93

Abstract

Age and growth, mortality, and exploitation level of the shield-head catfish Synodontis schall inhabiting River Nile, Egypt are studied to evaluate its fishery status and proposed some reference points for its sustainability. A total number of 805 specimens comprising of 306 males and 499 females with the size range of 16.7 - 37.8 cm TL (mean = 26.71 ± 3.58) were investigated. The weight of specimens ranged from 60.0 to 650 g (mean = 194.88 ± 26.58). Statistically, there is no difference between males and females in the longevity and population parameters so all parameters were estimated for sexes combined. The maximum life span of this species was 4 years based on the pectoral fin spine sections. Asymptotic total length (L∞) was 42.25 cm, growth coefficient (K) was 0.42 yr-1, and theoretical age at zero-length (t0) was -0.36 yr, while the growth performance index (Ø’) was 2.87. The instantaneous total, natural, and fishing mortality coefficients were 1.23, 0.54, and 0.69 yr-1, respectively. The Exploitation rate (E) was 0.56. The body length at first sexual maturity (Lm) and mean selection length (Lc) were estimated at 24.1 and 23.6 cm, respectively. There is selective fishing mortality towards smaller fish sizes reflecting the adverse impact of fishing effort. Therefore, for management purposes, it is recommended to increase the length at first capture to maintain sufficient spawning biomass for recruitment and monitoring the exploitation level to control the fishing effort.

Highlights

The Nile is the longest river in the world, stretching north for approximately 4,148 miles from East Africa to the Mediterranean
The present study aims to estimate age and growth, size at first capture, size at first sexual maturity, mortality rates and exploitation, which are essential tools in the management of this fish stock
Age structure of the S. schall specimens collected from the Nile, as determined from sections of the pectoral spine, was consisted of four age groups ranging from 1+ to 4+ years (Fig. 2)

Summary

Introduction

The Nile is the longest river in the world, stretching north for approximately 4,148 miles from East Africa to the Mediterranean. The length of the Nile in the Egyptian borders is about 1532 Km. North of Cairo, the Nile splits into two branches (or distributaries) that feed the Mediterranean: the Rosetta Branch to the west and the Damietta Branch to the east, forming the Nile Delta (Fig. 1). Small scale fisheries play an important role in Egypt's economy and are the source of livelihood for many people in the coastal areas. Inland fisheries based on rivers, lakes, reservoirs which are small scale fisheries are very important fishery resources in Egypt. The Nile provides a rich and vital habitat for estuarine and freshwater fish species and their regeneration in Egypt, where about 12% of Egyptian fish production was harvested from it (2005 – 2011) decreased to only 3.8% in 2019 [1]. Few studies were focused on the stock assessment as well as fish population dynamics of Nile fishes [2-9]

Results

Discussion

Conclusion