¿Qué son las agregaciones reproductivas? / What are spawning aggregations?
Uncategorized — octubre 20, 2005 01:21
Publicado por Alfonso Aguilar-Perera
La primera definición formal ofrecida por Domeier & Colin (1997) las identifica como “grupos de peces con-específicos reunidos con el propósito de desovar presentando densidades considerablemente altas comparadas con aquellas encontradas en el área de agregación durante períodos no reproductivos”. Sin embargo, Claydon (2004) considera que la definición de Domeier & Colin quizá sea restrictiva, por lo que ofrece una definición alterna como “cualquier agregación temporal formada por peces que han migrado debido al propósito específico de desove”. Asimismo, la Sociedad para la Conservación de las Agregaciones de Peces las define com “agrupaciones de especies individuales de peces arrecifales que se han reunido en grandes densidades que en condiciones normales con el propóstio específico de reproducción”. Por tanto, bajo las definiciones anteriores ¿podría considerarse como una agregación reproductiva la agrupación de al menos 3 peces, digamos, serránidos, reunidos durante la luna llena de diciembre? Asimismo, ¿podría considerarse como una agregación reproductiva la agrupación de 3 peces, pero ahora, digamos lábridos, durante la época de reproducción?
The first formal definition offered by Domeier & Colin (1997) identify a spawning aggregation as “a group of conspecific fish gathered for the purpose of spawning with fish densities or numbers significantly higher than those found in the area of aggregation during non-reproductive periods.” However, Claydon (2004) considers such definition by Domeier & Colin may be restrictive, thus he offers another definition as “any temporary aggregations formed by fishes that have migrated for the specific purpose of spawning.” Likewise, the Society for the Conservation of Fish Aggregations defines “a reef fish spawning aggregation is a grouping of a single species of reef fish that has gathered together in greater densities than normal with the specific purpose of reproducing.” Consequently, regarding such definitions, could a grouping of at least 3 fishes, say Serranids, gathered during full moon of December be a spawning aggregation? Likewise, could a grouping of 3 fishes, say Labrids, gathered during the reproductive season be a spawning aggregation ?
Domeier, M.L. & P.L Colin. 1997. Tropical reef fish spawning aggregations: defined and reviewed. Bulletin of Marine Science 60: 698–726.
Claydon, J. 2004. Spawning aggregations of coral reef fishes: characteristics, hypotheses, threats and management. Oceanography and Marine Biology: An Annual Review 42, 265–302. R. N. Gibson, R. J. A. Atkinson, and J. D. M. Gordon, (Eds.)
http://www.scrfa.org/server/spawning/index.htm. About spawning aggregations. downloaded 19 October 2005.
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2 Comentarios
I strongly believe that a group of 3 individuals can represent a spawning aggregation. I give a hypothetical example to illustrate why: a spawning aggregation of 10,000 Nassau grouper is found one year, but is then fished heavily over successive years. The aggregation declines in size until one year no fish migrate to the aggregation site. At what number of individuals should one declare that an aggregation is no longer being formed? Is a group of 3 individuals still a spawning aggregation? The aggregation may appear to be very different during its decline from 1000′s of individuals, and the way in which individuals behave at the aggregation may differ at lower number of individuals, but essentially the same phenomenon is occurring regardless of the number of individuals involved. Because the word “aggregation” means a group of 3 or more elements, any temporary aggregation formed by fishes that have migrated for the specific purpose of spawning, whether that be a group of 3 individuals or a group of more than 100,000, should be referred to as a spawning aggregation. Spawning aggregations are found along a continuum that represents the number of individuals that migrate to spawn together: at the lower end you have 2 individuals, and above this you find spawning aggregations. Any other lower limit to aggregation size is purely arbitrary and therefore inappropriate.
However, I understand that there may be a number of reasons why researchers may be reluctant to acknowledge this, not least of which because it appears to “devalue” spawning aggregations. It may also allow species whose behaviours do not fit the traditional perception of that which constitutes a spawning aggregation to be classified as such. However, in order to try to understand spawning aggregations it is counterproductive to ignore many species that form aggregations at the lower end of the continuum. Without also considering these, you cannot hope to put the enormous aggregations formed by some species in their proper context.