Hawai'ian Yellow Tang Population increase since 1999

[Timfish]

This report is three years old now but table two and table three show the population increases with Yellow Tangs and non aquarium fish from 1999 to 2009 off the west coast of the island Hawai'i. It' also gives a pretty interesting history of the issues around collecting aquarium fish of the west coast of the island Hawai'i. One important note is the research for this report was conducted by three different universities, two governmental agencies and the World Wildlife Fund

http://hawaii.gov/dlnr/dar/pubs/ar_hrs188F5v2.pdf

(This certainly requires much more research but one curiosity looking at the census numbers for the different species of tangs collected shows some species have larger populations in the areas where collection is allowed than in the protected areas. Since this is opposite of the Yellow Tang and Kole Tang populations is there some incompatibility between them or is there some mechanism(s) in the ecosystem that regulates the over all combined populations? Both?)

A chart showing the changes in yearly Yellow Tang population census including the 2010 is here:

http://hawaiibanfactcheck.org/wp-content/uploads/2012/02/YT-Abundnace-Change2.jpg

New rule changes by the Hawai'i Department of Land and Natural Resource, Division of Aquatic Resources states unlimited numbers of Yellow Tangs between 2" and 4 1/2" can be collected but no more than 5 per day can be collected smaller than 2" or 5 per day larger than 4.5". Bear in mind there are restrictions and permits required for nets used by collectors and there are practical limits on scuba diving.

http://files.hawaii.gov/dlnr/meeting/submittals/130628/F-DAR-Submittals-F2.pdf

An interesting website for those interested is the website for the Division of Aqoatic Resources here:

http://hawaii.gov/dlnr/dar/index.html

[(Bio)³]

Now if we can just get the long nose black tang population up!

[jestep]

I wonder if ocean acidification and warming, which is also well observed, and thus accelerated growth of algae is also a contributor.

[Timfish]

There's also the loss of the sharks. Removing apex predators from an ecosystem always screws it up by letting herbivores populations get out of balance. (Bio³) The Long Nose Black Tang, Zebrasoma rostrum, isn't collected in Hawai'i, the Black Surgeonfish the report is referring to is Ctenochaetus hawaiiensis what I'm familair with as the Chevron Tang.

[subsea]

Tim,

To what do you attribute the decline in the shark population?

Patrick

[+brian.srock]

Shark Fin Soup

[jestep]

Humans...?

Worldwide shark populations are 10% of what they were about 20 years ago. Not sure how Hawaii's regional numbers are doing.

[Planeden]

could it just be the ebb and flow of preditor/prey relationships. you can see it here in austin with the bats and crickets. some years, lots of bats and no crickets. bats starve, population decreases, then you get lots of crickets and no bats. bats repopulate and the cycle continues.

[mFrame]

[jestep]

Forgot about that one, great graphic.

The sharkwater documentary is a huge eye opener.

[Planeden]

ok, so probably not just non-human preditor/prey then. that's a lot of frigging sharks.

[Timfish]

A lot are killed as bycatch in nets and are just discarded. Some are species are severely overfished (a few species to extinction) and some species are quite stable.