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Human noise may be scrambling the eggs of baby fish

Whether it’s cargo ships, oil rigs, or sonar, humans make a lot of noise in the ocean. This cacophony can disorient fish and make them more vulnerable to predators. Now, for the first time, researchers have revealed that noise pollution can meddle with these sea creatures even before they hatch.

The team focused on two species of damselfish common on Australian coral reefs: spiny chromis (Acanthochromis polyacanthus) and the red and black anemonefish (Amphiprion melanopus, pictured). Both are fairly easy to rear in the lab and they differ in the ways their embryos develop. In the lab, the researchers watched the offspring of these fish mature under audio recordings of either ambient reef sounds, or reef sounds with motorboats passing overhead every 5 minutes. They monitored the embryos’ heart rates, yolk sizes, and physical characteristics.

Undersea din can warp baby reef fish development, the team reports this month in Marine Pollution Bulletin. The embryo hearts of both fish beat 10% faster when boat noise was played, and the spiny chromises exposed to the racket hatched about 5% larger than those under ambient noise; their eyes were also about 9% larger.

The researchers think the stress produced by boat noise may boost embryo metabolism, draining yolk energy reserves and forcing the embryos to grow faster. Indeed, chromises reared with boat noise had yolks 13% smaller than their ambient counterparts at hatch time. Smaller yolks may mean less energy available to newly hatched, growing larvae.

The scientists say it’s still not clear whether any of these changes are detrimental to the fish. If they are, they say, noise pollution may be having an even more insidious impact than previously believed.