definition of spawning aggregations and related terms. --- spawning aggregation. in general terms, we define a spawning aggregation as a group of conspecific fish gathered for the purposes of spawning, with fish densities or numbers significantly higher than those found in the area of aggregation during the non-reproductive periods. for fishes which normally occur in dense schools (i.e. Carangidae), fish in a spawning aggregation must occur in significantly greater number and teke up significantly more space than non-reproductive fish.