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The role of nursery habitats and climate variability in reef fish fisheries in the Gulf of California

The role of nursery habitats and climate variability in reef fish fisheries in the Gulf of California
MARCO OCTAVIO ABURTO-OROPEZA

2009

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, UNITED STATES OF AMERICA.

ABSTRACT

One of the most important services that coastal habitats supply is the provision of seafood that feeds people and supports local fishing economies. Despite this importance, there has been little analysis of the ecological processes that contribute to the local economies, and the impact that human activities have on these processes. The objective of this thesis is to study the relationship between coastal habitats and the dynamics of commercial reef fishes in the Gulf of California, and estimate the value of the services these habitats provide for fisheries. In the first section I will describe the interconnections between the life history of yellow snappers and leopard groupers, and their major nursery habitats (mangrove forests and Sargassum beds, respectively).

In the second section, beyond recruitment, I will explore whether all mangrove patches contribute equally to maintaining adult fish populations. I will study the relationship between juvenile snapper abundance and the amount of suitable mangrove nursery area, and estimate the contribution of mangrove patches of different sizes to the replenishment of fish populations.

The last section includes fishery statistics for both species, and an economic valuation of mangrove ecosystems for the entire Gulf of California. I will analyze yellow snapper and leopard grouper abundance and fishery data, to determine whether it is possible to predict fish recruitment and landings based on available a priori climate indices. In the final part of this thesis I will test the hypothesis that the amount of mangrove forests has a direct bearing on the production of many commercially important fisheries.

The results of this thesis show that the life history characteristics of two of the most important commercial reef fish species in the Gulf of California are affected by the impact of climate variability on their nurseries. I determined that the Multivariate ENSO Index (MEI) explained the abundance of juveniles and fisheries landings for both species; increasing recruitment translated into greater fisheries landings once individuals recruited into fishing stocks. I also showed that standard underwater visual surveys combined with traditional fisheries statistics could provide a model to predict fluctuations in abundance over time, and could be used to adapt artisanal fisheries management ahead of time, regulating effort or setting quotas based on expected climate-mediated recruitment of fish into adult populations.