# Seasonal fish larvae abundance and composition in seagrass habitats of coastal East Africa

## TL;DR

This study explores seasonal fish larvae abundance in seagrass habitats along East Africa's coast, revealing patterns influenced by hydrodynamics and productivity.

## Contribution

The study provides new insights into seasonal fish larvae dynamics in seagrass habitats across Kenya and Tanzania.

## Key findings

- Fish larvae abundance was highest in Kenya during the northeast monsoon season.
- Primary productivity and dissolved oxygen are positively linked to fish larvae productivity in both regions.
- Most fish species spawn year-round in tropical waters, with no strong seasonal patterns observed.

## Abstract

Seagrass habitats play a major role in fisheries productivity through nursery functions and feeding grounds for diverse fish species. However, little is known about the seasonal distribution of fish larvae at large spatial scales in coastal East Africa. We investigated drivers of the seasonal fish larvae abundance and composition in seagrass habitats in Kenya and Tanzania. We found a high diversity of fish larvae (54 families) inhabiting seagrass habitats that differed between sites and seasons. Fish larvae abundance were highest in Kenya, particularly during the northeast monsoon season. Overall, total larval abundances per site were low, reaching less than 190 individuals/100 m3 in Kenya and less than 40 individuals/100 m3 in Tanzania, likely related to the low productivity and strong hydrodynamic processes in this region. Our data suggests that most of the fish spawn year-round in these tropical waters as we did not find strong seasonal patterns. All sites had a high relative abundance of larvae from demersal spawning fishes, indicating that many fish species move to coastal sites for spawning. Primary productivity and dissolved oxygen, driven by hydrodynamics conditions are positively related to fish larvae productivity both in Kenya and Tanzania. These findings indicate that the occurrence of both resident and transient fish larvae in seagrass meadows is driven by strong hydrodynamic and tidal processes that transport fish larvae across adjacent habitats.