Title: Application of length-based spawning potential ratio method and analysis of the structure of the electronic catch assessment survey in marine waters of mainland Tanzania.

In fisheries management, reliable and accurate information is important for good decision making. The objectives of this study were to assess the applicability of LB-SPR as a tool for fisheries management at a small-scale and asses the electronic catch assessment survey in marine waters of mainland Tanzania. This study identified the use of mobile phones as an important tool for improving data collection. In general, for the tuna and tuna-like species, the larger species were represented as immature fish in the catches and subsequently, the estimated SPR was low. However, the smaller tunas were generally caught after or during maturation and their SPR values were higher. Three species of reef fishery were found to have less than 20% SPR. The results could have been affected in some cases by a few numbers of samples and inaccuracy in measuring the length of fish and identification. Structure of the frame survey data and catch assessment survey was revised and a more efficient and robust stratification of the structure of crafts and their associated gears was developed, hence reducing the complexity. The percentage of missing landings due to absence or inconsistency of crafts-gear combination in the eCAS system was estimated to be 17%. The estimated total catch of six months (June – November) for marine waters in 2019 was 59,912 metric tons, for the whole year it can lead to landings of 120,000 metric tons.