On Lunar Periodicity in Spawning of normally grown Falmouth Oysters (O. edulis) in 1925, with a comparison of the spawning capacity of normally grown and dumpy Oysters.

Abstract

During 1925 dumpy oysters spawned in a high proportion on the Fal beds, and although not such heavy breeders as normal oysters, they are undoubtedly valuable in forming a stable spawning stock for replenishing the beds in the future. Nearly every normal and dumpy oyster above a size of 2 to 2\ inches produced at least one batch of spawn in 1925. Since dumps increase in proportion on the beds as over-fishing occurs, they form a natural breeding reserve for repopiilating the beds in favourable years, as there is no adequate reason to suppose that the larvae of dumps are unhealthy. Weekly samples of oysters examined closely during the summer of 1925 for the percentage of spawning females and ripe but unspawned females show