Larval fish production and dispersal in critical habitats of coastal East Africa (FLAPSEA)

Kenya Marine and Fisheries Research Institute (Kenya; Lead Institution); Institute of Marine Science, University of Dar es Salaam (Tanzania) & Stockholm University (Sweden)

Project Collaborators: 

James Mwaluma (Kenya Marine and Fisheries Research Institute), Monika Winder (Stockholm University, Department of Ecology, Environment and Plant Sciences, Sweden, Margareth S. Kyewalyanga (Institute of Marine Science/University of Dar es Salaam, Tanzania), Mwanahija Shalli (Tanzania Fisheries Research Institute), Barnabas Tarimo (Institute of Marine Science/University of Dar es Salaam, Tanzania), Rushingisha George (Tanzania Fisheries Research Institute), Melckzedeck Osore (Kenya Marine and Fisheries Research Institute), Jacob Ochiewo (Kenya Marine and Fisheries Research Institute), Lillian Daudi (Kenya Marine and Fisheries Research Institute), Charles Muthama (Kenya Marine and Fisheries Research Institute), Noah Ngi’siange (Kenya Marine and Fisheries Research Institute), Fadhili Malesa (School of Aquatic Science and Fisheries, University of Dar es Salaam).

The project aims to understand to what extent food-provisioning services in the form of fish larval production are threatened by habitat degradation and fragmentation, and how production of this natural resource is related to climate change and development in the coastal WIO region.

Specific objectives include

1) Identify habitat conditions critical for fish recruitment and key drivers for fish larvae production.

2) Identify dispersal potential of fish larvae from the seagrass habitats where adult fish spawn.

3) Use this information to predict future economic impacts and the most vulnerable coastal areas.

4) Provide scientific information that can lead to improved management and protection strategies in coastal East Africa.

• The project will generate at least (6) scientific publications in peer reviewed journals by   the end of the project.
• Generation of (2) seagrass habitat maps. One for Kenya and Tanzania
• Generation of (3) Policy briefs in Seagrass habitat health, Fish habitat function and seagrass management,
• Manual for monitoring seagrass degradation (1)
• Generation of (1) model predicting the effects of seagrass habitat destruction to the nearshore ecosystem of fish larvae and effects on the overall fisheries.
• Generation of (4) M.Sc. and (1) Ph.D. degrees during the lifespan of the project.
• Short documentary (2) on larval dispersal and settlement in seagrass habitats (Swahili and English)
• Presentations (4) in the 13th WIOMSA symposium (2021)

• Identify seagrass health status in KE & TZ
• Identify causes for degradation if any.
• Quantify fish larvae diversity and abundance in seagrass areas
• Investigate fish larval body conditions
• Identify major food sources for selected fish larvae.
• Investigate larval dispersal distance from seagrass beds to coral reefs,
• Assess scales of habitat connectivity of two fish species
• Model construction to evaluate: How future habitat destruction will affect fish recruitment; How shallow vegetated waters will contribute to larval supply & Critical seagrass habitat degradation thresholds to sustain ecosystem services
• Provision of different seagrass management and conservation strategies
• Stakeholders engagement
• Dissemination of information best-case scenarios

Summary of the Key findings

• Chlorophyll exhibited strong seasonal variations with higher chlorophyll-a during the South East Monsoon (SEM) and interannual variability within the seasons in both countries. In Kenya, significant differences found between sites (Watamu>Diani), however in Tanzania no significant variation found between sites, but significant seasonal differences were found (SEM>North East Monsoon <NEM>).
• Phytoplankton density followed a similar trend as chlorophyll-a in Kenya with higher densities occurring in Watamu as compared to Diani though not significantly. Interannual variability was noted between seasons while overall average density (irrespective of the season) was higher in healthy sites as compared to degraded sites
• Zooplankton density showed no significant differences between healthy vs degraded in both countries. However significant (p<0.05) seasonal differences occurred in Kenya in both Watamu and Diani (NEM>SEM )
• Fish eggs showed no significant differences by season and by status (healthy vs degraded) and this follows the complex nature of spawning habits of fish. No clear pattern was observed as there was high fish egg abundance in both healthy (Watamu NEM) and degraded sites (Diani SEM) showing fish spawning was continuous during SEM and NEM.
• Fish larvae were abundantly distributed in heathy sites as compared to degraded sites in both countries. No significant differences occurred between sites and seasons in Tanzania, however, significant seasonal differences were found in Kenya (NEM>SEM). Higher fish larvae were encountered in Watamu compared to Diani.
• Seagrass cover was higher in healthy sites in Tanzania at both sites while in Kenya per cent seagrass cover similarly was highest in healthy areas both during SEM and NEM.
• Shoot density showed a similar trend with higher shoot density in heathy sites in both Kigombe and Mwarongo. Similarly in Kenya shoot density was highest in heathy sites as compared to degraded. Higher shoot density was found in Diani site which was colonised by two species T. hemprichii and T. ciliatum while Watamu had several pioneer species indicating some level of disturbance.

i) Lilian Nduku (PhD-student) – Seagrass diversity, distribution and production

ii) Noah Ngisiang’e (PhD-student) – Global Information System mapping of seagrass, currents, fish larvae and plankton trajections

iii) Alphine Mbodze (MSc-student) – Diversity, abundance and distribution of zooplankton and fish larvae in relation to environmental variables.

iv) Helen Kizenga (MSc-student)

v) Barnabas Tarimo (PhD-student)

vi) Fadhili Malesa (MSc-student)

vii) Oliver Ogola (BSc-student) – Water quality, nutrients levels, BOD, DO, Chlorophyll

viii) Jibril Olunga (BSc-student) – Beach seine contents, finfish, shellfish, larval stages and diversity

Dr James Mwaluma

Email: jamesmwaluma@gmail.com