And they call it guppy love . . . howmale fish serenade their mates

Amorous cod go in at deep end by grunting and singing at night

Cod you believe it – male fish serenade their mates?

Scientists in the west Highlands have found they sing to the females during the spawning season – and that night-time is the right time for fishy romance.

Researchers from the Scottish Association for Marine Science, ( Sams) near Oban, looked at the love lives of cod and pollack.

They found males from both species “grunt” for 15 minutes at a time to attract females in the shoal.

PhD student Lindsay Wilson said it is believed they choose amate with the deeper sounds.

Miss Wilson said: “We found the cod grouped their loud periods of grunting in bouts of about seven.

“The fish were not just making more grunts ad hoc, they were being produced in a rhythmic manner, in a pattern.”

She added: “The physical structure of sound being produced was different during a period of high grunt. The dominant frequency of the sound was lower, the repetition period increased and each grunt

“Multiple males are competing, like a chorus”

got longer. This change is dramatic so it indicates that something is happening. It’s an important time, the fish are pushing themselves and investing more to produce these sounds.

“It could be that they’re encouraging a female who is making a mate choice."

Researchers studied two populations of fish caught separately in the Firth of Clyde and in the Sound of Arisaig, and held in indoor tanks at a fishery in Argyll.

Up to two thirds of the grunting happened at night, with both species peaking after 15 minutes and then pollack would take a 45-minute break to recover, while cod took up to an hour.”

“It could be thatmultiple males are competing, almost like a chorus,” the researcher said.

The pollack’s grunt had never been recorded until now, the paper in the Journal of Fish Biology noted.

Miss Wilson, who is now working at the Sea MammalResearchUnit at StAndrewsUniversity, said: “‘We alreadyknewmalecodproduce these sounds, we just wanted to dig a bi t deeper.”