Effect of artisanal fishing and water pollution on the stock of Bagrid catfish (Bagrus meridionalis) in the northern part of Lake Nyasa/Niassa/Malawi in Tanzania: An insight from Nyasa district

<h2>Abstract</h2> The critically endangered <i>Bagrus meridionalis</i> is one of the large fish species endemic to Lake Nyasa/Niassa/Malawi. Its population from the southern part of the lake, in Malawi and Mozambique, has declined by over 90 % within 10 years from 2006 to 2016 due to overharvesting. Despite that less is known from the northern part of the lake in Tanzania where studies on <i>B. meridionalis</i> population dynamics and trends are conspicuously missing. This is affecting effective monitoring and sustainable management of the species in this part of the lake. The lake is also under the influence of unsustainable agricultural practices in the lake basin which are thought to pollute the lake. However, it is also not known how this has affected the growth and survival of the fish in the lake. We, therefore, investigated the effect of artisanal fishing and anthropogenic pollution on the status of the stock of <i>B. meridionalis</i> in the northern part of Lake Nyasa/Niassa/Malawi in Tanzania using the catch per unit effort technique, length-frequency distribution, and relative condition factor. We sampled water and fish, and measured fish standard lengths, weights, and levels of water physical-chemical variables. We found that the stock <i>B. meridionalis</i> population in the northern part of Lake Nyasa/Niassa/Malawi is very low and is experiencing recruitment overfishing with most of the fish being caught while immature. Despite this, the caught fishes had good body condition indicating that they are surviving in a favorable ecological environment. Urgent mitigation measures are therefore required to halt overfishing to safeguard community livelihood and the endangered <i>B. meridionalis</i>.