A spatial multivariate approach to understand what controls species catch composition in small-scale fisheries

Many multivariate methods have been applied to small-scale fishery data in an attempt to distinguish factors that characterize the fishing activity and influence catch composition. While such approaches are important, they are still incomplete for including the spatial structuring in the analysis, a non-random fundamental and functional component of the ecosystem. This study fills this gap by identifying, describing, and quantifying factors that influence the fleet type of tropical small-scale fisheries using a multivariate spatial approach. The example data came from two Brazilian States where two main fleets, open water canoes and motorized boats, operate. Different complex combinations of fishing, environmental and spatial factors affect the structure of the fish catch composition of each fleet. Motorized boats showed strong spatially-structured species catch composition in comparison with open water canoes. Similar environmental factors, such as type of the seabed and depth, but different fishing variables (gear vs crew size), affected the species catch composition of these vessel categories. Despite some overlap, each fleet focuses on a relatively distinct set of species groups and exploits habitats at different spatial scales. These results suggest that different sets of regulations should be considered for each fleet type within a specific spatial scale. It also shows that multi-species models that aggregate groups of species is a more efficient alternative than single-species assessment models for small-scale fisheries, as these are multi-specific and multi-gear, with scattered landing harbors, features that make such fisheries a complex challenge for management.