Abstract

Nassau grouper participate in mass spawning aggregations one to three times each winter for a period of approximately 10 days. During this time the density of fish on the spawning site is extremely high (~3000/ha on Little Cayman Island). Based on previous observations, spawning grouper spend a large portion of their time being cleaned, which indicates this is an important activity during the spawning period. Competition for cleaning stations on the aggregation site may therefore intensify when the additional biomass of Nassau is present, if cleaning stations are a limiting and desirable resource. Each morning during the aggregation periods of 2006 and 2007, we used digital video to record cleaning behavior at a centrally located spawning-site cleaning station on Little Cayman Island. We set the camera approximately 2m from the cleaning station and allowed it to run for the duration of a 90 minute tape. Cameras were retrieved in the evening. Videos were then post-processed to determine (1) the size of clients, (2) duration of time each client spent being cleaned, (3) intra-and interspecific interactions, and (4) color phase shifts of the clients coincident with interactions. Cleaning station interactions were clearly linked to color phase shifts, suggesting that the color phases of spawning Nassau grouper are highly dynamic and do not exclusively connote reproductive status. Competition and size-based dominance at the cleaning station indicated that cleaning stations are a limiting resource to Nassau grouper during the spawning season, and competitive dominance at the cleaning station may confer competitive advantage in spawning.

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