A new study suggests when anglers might have the most lunar luck.
Research Need
Various fish species have always experienced the lunar cycle’s effect. Scientists have conducted multiple studies on fish migration, spawning, and feeding behaviors in relation to the cycle. These studies show highly complex patterns across a wide diversity of species.
A new review of previous research focuses on identifying common patterns of lunar effects on large, surface-level species — specifically tuna, billfish, sharks, and rays.
What did they study?
Scientists searched several sizable databases for previous research and then recorded key pieces of information, including species, lunar measurements, and study location. Each study was carefully evaluated by a minimum of two team members. Altogether, the team reviewed 190 studies.
The studies encompassed many disciplines and types of measurements. Shark studies often focused on movement, while tuna and billfish studies were primarily the subjects of fisheries science. Overall, most of the studies focused on billfish, with swordfish the most studied billfish species
What did they find?
Many studies had used electronic tagging methods of various kinds. Slightly over half (51%) showed fish swimming into deeper waters as lunar illumination increased, and only 5% of the studies showed movement into shallower waters. This pattern was strongest in tuna species.
Although they displayed the same pattern overall, billfish and shark species showed more variability. For sharks, the results were more species-dependent, with four species moving into shallower waters as lunar illumination increased: the bull shark, Galapagos shark, oceanic whitetip shark, and the largetooth sawfish.
Shark, tuna, and ray species did not show a significant relationship between catch rate and the amount of lunar light. However, catch rate for swordfish increased as lunar illumination increased — although other billfish species didn’t show a similar trend.
Acoustic data revealed a few species-specific movement patterns based on moon phase, particularly in ray species. Spawning rates were also species-specific but with no noticeable patterns.
Many species showed activity changes throughout the lunar cycle. Most sharks showed increased activity during full moons, with some showing increased activity at new moons as well.
Predator-prey interactions, biological rhythms, tidal effects, and other factors may also influence these studies’ findings. In addition, a lack of consistency across data gathering methods and study goals would have impacted the results.
So what?
Understanding the effects of the lunar cycle on fish behavior can better inform fisheries managers. Synthesizing data like these scientists did from studies conducted on similar species under different circumstances can help identify commonalities, patterns, and correlations that increase understandings of this and other phenomena.
Reading
S. Andrzejaczek, A. E. DiGiacomo, C. S. Mikles, C. M. L. S. Pagniello, T. E. J. Reimer, B. A. Block. 2024. Lunar cycle effects on pelagic predators and fisheries: insights into tuna, billfish, sharks, and rays. Rev Fish Biol Fisheries. https://doi.org/10.1007/s11160-024-09914-7
The text from Hook, Line & Science is available to reprint and republish at no cost, but only in its entirety and with this attribution: Hook, Line & Science, courtesy of Scott Baker and Sara Mirabilio, North Carolina Sea Grant.
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