By-Catch Assessment and Mitigation in the Western Indian Ocean (BYCAM)

While there are considerable industrial marine fisheries in the south-western Indian Ocean (SWIO),  notably for tunas and crustaceans, regional Small Scale Fisheries (SFF) are of greater social importance,  employing > 0.5 million fishers and contributing > 70% of regional marine fisheries’ catches. Despite often  being overlooked, SSF may impact marine ecosystems, thus they reflect the global challenge of balancing  conservation goals with communities’ dependence on marine resources. Marine megafauna  (elasmobranchs, marine mammals and sea turtles) are vulnerable to fisheries, and play important roles in  marine ecosystems. Yet, little is known of the interactions between SWIO SSF and these species. This lack  of information was the main driver for the WIOMSA/MASMA funded BYCAM project. The overall aim of  BYCAM was to provide for future sustainable fisheries by creating a baseline estimate of current marine  megafauna exploitation and subsequently develop and test methods for mitigation of vulnerable  megafauna catches, and to provide recommendations for future governance and management. BYCAM focussed on three fisheries with known bycatch problems: semi-industrial prawn trawls, and small scale coastal longlines and gillnets.

BYCAM provides a much needed first independent quantitative assessment of SFF catch in the SWIO region and demonstrates that current FAO data for elasmobranch catches are seriously underreported, whilst catches of both marine mammals and sea turtles are ongoing. The implication of catch underestimates in official data is that vulnerable elasmobranch species may be overexploited and further that the specialist livelihood strategies of those relying on this catch are under threat. The project also demonstrates the need for a multi-method approach towards assessing marine megafauna interactions with SSF in the SWIO and other data-poor areas. The low cost mitigation methods developed and trialled in the project to reduce bycatch of vulnerable megafauna are promising. Funding has been secured and new trials with the bottle alarm and acoustic reflectors are underway. Further, there is considerable scope for more wide-spread use and implementation of TEDs in SWIO prawn trawls. The project has taken the first steps towards building governance frameworks to promote sustainable fisheries management within the WIO.

The overall aim of this project was to provide for future sustainable fisheries by addressing bycatch in the WIO.  Specifically, this included assessment  of bycatch of large, non-target vulnerable  megafauna  species, provide realistic mitigation measures and recommendations  for governance  & management.  Thereby facilitating ecological and socio-economical  sustainable artisanal,  small-scale  commercial  and semi- industrial fisheries in the WIO. Vulnerable  megafauna  are of particular  interest as they are extremely vulnerable to non-natural  mortalities  as a result of late maturity and low reproductive  rates, whilst being important for the stability of ecosystems.  The project focused on three types of artisanal,  small-scale commercial  and semi-industrial  fisheries with known bycatch problems:  prawn trawls and coastal longlines and gillnets (drift and bottom-set).  The work will be focussed in Kenya, Mozambique, Tanzania,  and Zanzibar with a small-scale  case study in Madagascar.

• To review current WIO fisheries monitoring  activities and their management  efficacy.
• The collection  and assessment  of prawn trawl and coastal gillnet and longline fisheries effort data in Kenya, Tanzania, Zanzibar and Mozambique, using official fisheries statistics and observer networks.
• Collection and assessment of bycatch data,  species and rates for elasmobranchs,  marine mammals  and sea turtles in coastal fisheries through use of observers & fisher networks.
• Evaluation  of existing bycatch mitigation methods where these exist.
• Evaluation of observed (using observers & fisher networks) bycatch composition  and rate against those reported through RBAs to assess reliability.
• Survey of socio-economic  importance  of species and perceptions  of stakeholders  towards these species including their non-consumptive value, their ecosystem importance and sustainability  especially under future scenarios of megafauna removal and likely impacts on trophic foodweb dynamics.
• Pros and cons of different  management  measures  considered  alongside policy,  governance,  socio-economic behavioural  drivers, markets and livelihood issues.
• Constraints  to management  mitigation measures and critical factors affecting  economic and social performance  indices will be identified and used to inform development  of good governance support and policy reform so they are developed at the same time and not at the end as an ‘add-on’.
• Collection  of life history parameter  data (age, growth curves, reproductive  capability,  age of maturity) for selected megafauna  species of high bycatch rate in order to perform  demographic  analysis and aid in stock assessment.
• Production of an ERA (productivity-susceptibility analysis) at the WIO scale based on RBA survey data, from semi-industrial,  small-scale  commercial  and artisanal fisheries
• For marine mammal species;  for those areas where data are available on population  abundance and genetic population  structure,  assessment of bycatch impact on respective population  will be conducted. Carry out a series of bycatch mitigation trials across fisheries in the region (TEDs, pingers, circle hooks and re-developed  methods);  assessing their efficiency and feasibility for broad scale implementation. Create an updatable  spatial database with further development  of a redistributable  and revised atlas, fact sheets and thematic maps detailing fisheries effort,  gear type,  species presence (in bycatch), levels of bycatch in gear type and areas of highest risk (stress areas) for species across surveyed fishing grounds within the WIO.  This will further serve to identify areas of critical importance  and areas in need of more extensive work in the future.
• Recommendations for bycatch assessment  and mitigation methods for respective  fishing gear for future sustainability and management.

1. BYCAM Final Report
2. Barrowclift E., Temple A.J., Stead S. Jiddawi N.S., Berggren.P., 2017. Social, economic and trade characteristics of the elasmobranch fishery on Unguja Island, Zanzibar, East Africa.
3. Temple A.J., Kiszka J.J, Stead S.M., Wambiji N., Brito A., Poonian, C.N.S, Amir O.A., Jiddawi N., Fennessy S.T., Perez-Jorge, S., Berggren P., 2018. Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management.
4. Pirog A., Jaquemet S., Ravigné V., Cliff G., Clua E., Holmes B.J., Hussey N.E., Nevill J. E.G., Temple A.J., Berggren P., Vigliola L., Magalon H., 2019. Genetic population structure and demography of an apex predator, the tiger shark Galeocerdo cuvier.
5. Pirog A., Ravigné V., Fontaine M.C., Rieux A., Gilabert A., Cliff G. Clua E., Daly R., Heithaus M.R., Kiszka J.J., Matich, P., Nevill J.E.G, Smoothey A.F, Temple A.J., Berggren P., Jaquemet S., Magalon H., 2019. Population structure, connectivity, and demographic history of an apex marine predator, the bull shark Carcharhinus leucas.
6. Salmin Y. , Jiddawi N., Gray T., Temple A.J., Stead S.M., Pirog A., Ravigné V., 2019. Improving bycatch mitigation measures for marine megafauna in Zanzibar, Tanzania
7. Temple A.J, Wambiji N., Poonian C.N.S., Jiddawi N., Stead S.M., Kiszkae J.J., Berggren P., 2019. Marine megafauna catch in southwestern Indian Ocean small-scale fisheries from landings data.
8. Temple A.J., Stead S.M., Jiddawi, N. Wambiji N., Dulvy N.K., Barrowclift E., Berggren P. , 2020. Life-history, exploitation and extinction risk of the data-poor Baraka’s whipray (Maculabatis ambigua) in small-scale tropical fisheries.
9. Yang L., Sharpe M., Temple A.J., Jiddawi N. Xu X., Berggren P., 2020.Description and classification of echolocation clicks of Indian Ocean humpback (Sousa plumbea) and Indo-Pacific bottlenose (Tursiops aduncus) dolphins from Menai Bay, Zanzibar, East Africa
10. Weigmann S., Gon O., Leeney R.H., Barrowclift E., Berggren P., Jiddawi N, Temple A.J. 2020. Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan
11. Wambiji. N, Kadagi N.I., Everett B., Temple A.J., Kiszka J.J., Kimani E., Berggren P., 2022. Integrating long-term citizen science data and contemporary artisanal fishery survey data to investigate recreational and small-scale shark fisheries in Kenya