Environmental influences on egg and propagule sizes in marine fishes

Fishes are diverse in their mode, location, and timing of spawning (Breder and Rosen, 1966). External fertilization is the dominant mode of reproduction in fishes, although internal fertilization occurs in approximately 500 of the more than 22 000 known species of fishes worldwide (Wourms and Lombardi, 1992; Nelson, 1994). At spawning, oviparous fishes either broadcast their eggs into the pelagic environment, release them near substrate, or deposit them in protected locations. From this point onward, the developing embryo may be transported hundreds of kilometres before hatching or may remain virtually at the site of fertilization, depending on the species’ spawning habits, the buoyancy and external morphology of its eggs, and the local environmental conditions (Cowen and Sponaugle, Chapter 15, this volume). Mortality losses during the embryonic period and continuing into larval life are extraordinarily high in marine teleosts relative to other vertebrate groups (McGurk, 1986; Bradford and Cabana, Chapter 17, and Houde, Chapter 6, this volume).