Lunar synchrony and reproductive strategies of intertidal-breeding fishes

When is the best time to breed? This is an important question, especially for fishes that breed in the intertidal zone, a dynamic habitat where conditions change rapidly and cyclically. Many intertidal fishes reproduce during the spring tides (during the new and full moons when tidal fluctuations are strongest). However, we use long-term field data to present a counter example, the toadfish, Porichthys notatus, which spawns more often during the neap tides (during the quarter moons when tidal fluctuations are weakest). We hypothesize that if a species’ reproduction involves time-consuming tasks, such as courtship, mate selection, nest preparation, and prolonged egg-laying, and if these activities must occur underwater, then such species will align their reproduction with neap tides rather than spring tides. To examine the prevalence of neap tide spawning, we conducted a comprehensive literature review to explore the diversity of reproductive strategies and timings in intertidal fishes. Because some species must leave the intertidal zone or find refuge when the tides recede, whereas others exhibit amphibious lifestyles and can even breathe air, we paid specific attention to different species’ requirements for submersion to perform their reproductive behaviours. We gathered data on 131 fish species and ultimately highlight a scarcity in data on reproductive timing in intertidal fishes. Our literature survey provides preliminary support for our hypothesis, and we now call on researchers to directly examine lunar synchrony of reproduction in intertidal fishes to better understand how reproductive strategies are shaped by the tides.