Spawning Aggeragations

BULLETIN OF MARINE SCIENCE, 72(1): 103–121, 2003

SPAWNING AGGREGATIONS AND REPRODUCTIVE BEHAVIOR OF REEF FISHES IN THE GULF OF CALIFORNIA Enric Sala, Octavio Aburto-Oropeza, Gustavo Paredes and Glenn Thompson
ABSTRACT
Spawning aggregations numbering up to tens of thousands of reef fishes have disappeared throughout the tropics due to fishing, causing the collapse of their populations and ofcommercial fisheries in many regions. Although there is a wealth of information on spawning aggregations in the Caribbean and the Indopacific, there are almost no data on spawning aggregations of commercial reef fishes in the Tropical Eastern Pacific. Here we describe aggregations and the reproductive behavior of eight species of reef fishes in the Gulf of California, Mexico. The serranidsMycteroperca prionura and M. rosacea, the snapper Lutjanus novemfasciatus, and the jacks Caranx sexfasciatus and Seriola lalandi form spawning aggregations of 12 to >1000 individuals on islands, exposed coastal rocky reefs, and seamounts. The serranids Paranthias colonus and the snapper L. argentiventris spawn in schools with densities similar to these during non-reproductive periods. We observedaggregations of the serranid M. jordani but did not observe spawning. Some spawning aggregations of these and other species (such as Epinephelus itajara and Stereolepis gigas) have now disappeared from the Gulf of California due to fishing. Our findings suggest the existence of undocumented spawning aggregations throughout the Tropical Eastern Pacific that sustain varied levels of fishing pressure. Thesespawning aggregations must be identified and protected in order to ensure the replenishment of fish populations.

Many species of reef fishes, including groupers, snappers, and jacks, aggregate to spawn at specific locations and times throughout the tropics (e.g., Johannes, 1978a; Carter et al., 1994; Carter and Perrine, 1994; Sadovy, 1994; Domeier and Colin, 1997). Fishers in the Indopacificand the tropical Western Atlantic have targeted these aggregations, and have accumulated a wealth of knowledge on the reproductive biology of reef fishes, often for decades to centuries (Johannes, 1978b, 1981; Sadovy, 1994). This traditional knowledge of fish reproduction served the purposes of making fisheries more effective as well as ensuring their sustainability, although in recent times thisknowledge made fish populations more vulnerable to over-exploitation. Presently, understanding the reproductive biology of fishes is of paramount importance to establish minimum catch sizes, when to implement closed seasons, and where to locate marine reserves. Marine reserves, if they are to ensure the viability of fish populations, need to include the places where fishes spawn (Carr and Reed,1993; Bohnsack, 1998; Dayton et al., 2000). The link between theory and application, however, has been hindered by the fact that these larval sources are not known for most species. Dismissing the use of these kinds of basic natural history data in fisheries management can result in accelerated depletion of exploited fish populations. The Nassau grouper provides an excellent Caribbean example of howregulations addressing minimum catch size failed by ignoring the fact that most of the fishery was carried out on spawning aggregations (DeLoach, 1999). Likewise, trawling in the Gulf of Mexico destroys habitat that is essential for the reproduction of the gag (Koenig et al., 1996). It is therefore imperative to understand where, when and how fish species repro103

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BULLETIN OF MARINESCIENCE, VOL. 72, NO. 1, 2003

Figure 1. Map of the Gulf of California, México.

duce in order to manage fisheries adequately and develop conservation measures that ensure the replenishment of vulnerable populations. Here we present the first description of the reproductive behavior of commercial reef fishes and report on spawning aggregations of reef fishes in the Gulf of California. The Gulf...