Spawning Aggregations

A wide range of reef fishes aggregate in large numbers to spawn, including many species from highly valued food fish families. See this new video released on to see why spawning aggregations are so vulnerable to fishing. In Kenya and the Seychelles we have undertaken research on spawning aggregations to understand how best to manage them and thereby help secure the livelihoods of fishers dependent on these species.
Reef fish species forming spawning aggregations are often highly mobile, with migrations to spawning sites ranging from a few to hundreds of kilometres. Targeted fishing of aggregations in the early stages of exploitation can generate very high catch rates and revenues, but it is generally believed that such levels of exploitation are unsustainable.

This research programme, which spanned Kenya, Seychelles and Zanzibar, was initiated because to study the potential impact of increasing fishing pressure on the stock status and health of spawning aggregations. The overall goal of the research was to address critical information gaps and develop robust scientific approaches for the management and conservation of commercially important species that aggregate to spawn in the WIO.

The research results are detailed in a book published in 2013 (WIOMSA-CORDIO spawning book full), and demonstrated the feasibility of using basic information from spawning aggregation-based fisheries to systematically evaluate management needs in data-poor contexts. This was achieved through a conceptual approach  that involved estimation of key aggregation and fishery parameters and the application of those parameters in a vulnerability assessment and a no take reserve (NTR) model for spawning aggregations.

Conservation initiatives would benefit from explicitly incorporating assessment and management of spawning aggregation-based fisheries. Moreover, conservation initiatives would benefit from avoiding the over-generalisation, lack of quantitative evaluation and ethical and validity issues that have sometimes emerged in other regions.

Clearly, the conservation imperative is influenced by the fact that most research to date has focused on the more vulnerable aggregative spawners such as groupers. However, recognition that some aggregative spawners are relatively resilient to fishing is needed and the socio-economic aspects of the system must be understood (Robinson et al 2011).

Upon verification of an aggregation-based fishery and when status information is lacking, it is necessary to consider taxa-specific vulnerability to fishing and the potential costs and benefits of both conservation and fisheries management approaches. The data-poor tools used in the study can provide rapid information in such contexts.

In Kenya this research has led to a community closure for one of the rabbitfish spawning aggregations studied.