Questions about the open ocean

[DavidPT40]

Do any baitfish live soley far out to sea (the middle of the atlantic for example)? I always hear that this part of the ocean is referred to as a 'vast desert'.

How do tuna feed? I know that some schools migrate from the Med to the East Coast of the U.S. Do they break away from the school individually, or do they participate in mass feeding attacks?

Is plankton production high enough in the middle of the ocean to support fish?

 

[archman]

Do any baitfish live soley far out to sea (the middle of the atlantic for example)? I always hear that this part of the ocean is referred to as a 'vast desert'.

First, define "baitfish". There are lots of pelagic fish groups.

How do tuna feed? I know that some schools migrate from the Med to the East Coast of the U.S. Do they break away from the school individually, or do they participate in mass feeding attacks?

Beats me. But they eat a lot, and move fast. Check fishbase.

Is plankton production high enough in the middle of the ocean to support fish?

It's okay for larval fish. But generally the surface plankton in low latitudes is pretty sparse... that's why the water's so clear. As you get into more temperate waters, plankton density increases. And way up in the boreal provinces there's often enough of the stuff to support large filter feeders like rorquals.

Surface water biomass is poorest in the subtropics and tropics, except in upwelling or coastal zones. You'll still find fish, but few of the filter-feeding type (i.e. herring). Exceptions are things like mantas and whale sharks. Selective planktivores like chromis are common on reefs.

 

[DavidPT40]

Thanks for the info. When I was referring to baitfish, I meant small fish, like these sardines that Bronze Whalers are feeding on.

 

[drbill]

Baitfish are plankton feeders. I don't spend much time in blue water (well except when crossing from Catalina to the mainland). However the open ocean over deep basins generally lacks the nutrients required to produce significant plankton densities and therefore there would usually not be much food for the baitfish to eat. They are much more common in waters over shallow bottoms where nutrients are more readily upwelled into the upper water column where sunlight is sufficient for phytoplankton.

 

[archman]

Wasn't this last year's Best Photo of the Year or something?

 

[Supernal]

Wow, great picture! I knew sharks did "round-ups" but have never seen it!

 

[Diver0001]

Wasn't this last year's Best Photo of the Year or something?

Doug Perrine won something like nature photographer of the year for the series. He has a website with some out of this world pictures on it.

R..