(Madagascar) Building local population models of Octopus cyanea

Fieldwork in Madagascar required

Our understanding of the O. cyanea fishery, and how best to manage it, depends on our understanding of the dynamics of the local O. cyanea population. Current work has highlighted the seasonalities present in gonadal cycles, recruitment, etc. in the fished population, but has yet to examine much of the unfished population. As O. cyanea are likely to disperse as larvae on a scale much larger than a single closure or village’s fishing area, understanding the unfished population dynamics may be key to understanding the population’s sustainability. Information on two key parameters would greatly add to the current landings data and allow the construction of better population models:

Parameterising:

i. Local O. cyanea growth model – While O. cyanea growth models exist, the growth curve varies dramatically from location to location and the most comparable site is currently Senegal. To better understand O. cyanea population dynamics and how to best design a rotating closure system it is important to have an accurate model of O. cyanea growth that is applicable locally. This project involves mark and recapture of O. cyanea in the region, and will likely coincide with sub-tidal surveys. The student should have a background in biological sciences, be a certified diver, and be willing to live in Andavadoaka.

ii. Regional O. cyanea genetic connectivity – perform nested regional sampling and collaborate with molecular ecologists to determine if the local O. cyanea population is acting as distinct stocks or a single biological population. This has very important implications for reserve design.

Population modelling:

iii. Build local population models / reserve design models: These projects could be very open ended, ranging from the full stock assessment model that is currently being designed to very simple harvest models to assess optimal reserve designs. In these cases, the student would work with BV staff to incorporate the data generated in other projects and the landings dataset to ask the questions: What is the benefit of the closures on O. cyanea landings and/or population sustainability? Is the single seasonal closure optimal for harvest/ population sustainability? What would happen if sub-tidal populations were also harvested? etc.