Archive for November, 2017

Barramundi display individual movement patterns

Northern Territory barramundi display individual behaviour

Research is revealing the secrets of individual barramundi behaviour

Individual barramundi behave very differently.
And that’s not a fishermen’s thought, that is the finding of barramundi researchers.
Fishermen catch chromies (saltwater barra) at river mouths when there’s other chrome fish biting 50km upstream.
The research team explained after a four-day Roper River trip: “After downloading bulk acoustic tracking data, we were amazed by the behaviour of the tagged barramundi.
“Movements were tracked by automated listening stations placed at intervals from 5km offshore of the estuary mouth all the way upstream to Mataranka.
“Since the project began in late 2015, our 40 stations have recorded more than 2.6 million detections from more than 180 tagged barra, ranging from tiddlers to metre-plus fish.”
Star performers included a 630mm fish detected 10,065 times on 28 logging stations. It moved over a range of 185km, including large-scale movements within that range.
And yet another fish of 670mm fish stayed at one location over a 16-month period, with 44,079 detections from that location and nowhere else.
In between these extremes were all kinds of movement patterns, showing that while barra will move together in numbers, there are individuals that do their own thing.
“No wonder it is hard to work out what barra are doing and how to catch them,” researchers said.
Rain will trigger barramundi movement, and there’s been heavy early rain falling across the northern Top End.
For example, on Wednesday, 72mm was recorded at the top of the South Alligator catchment, with 45mm on the coast at Point Stuart.
On the same day Darwin region stations recorded falls to 54mm.
An early start can be a huge boost to the productivity of a wet season, if it keeps raining.
It might mean another big mob of small fish, and another future strong year-class for Top End fishos.
Two consecutive year classes are a good result, because if strong year-classes are years apart there would be more cannibalism by the larger fish.
Once the fingerlings of 2018 have six months to a year’s growth in them, they should be too big for the 2017 mob to eat.

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