Tang Research in Hawaii

[gobyvin]

http://0-departments.oxy.edu.oasys..../Claisse_et_al.2009_YT_Age_Growth_Habitat.pdf

Hello All,

I post this with no intention to start a debate, just to post information that I feel aquarists should know. I am a fisheries biologist (for the last decade and am completing a Master's Degree in fisheries science. I own a 180 gallon mixed reef with over 100 gallons of sump space and surge buckets / refugia. Most of my specimens live years. My best record to date is a royal gramma 14 years in my care. I have been FOWLR since I was 17 and I am 33 in Feb'11. I have been reefing for 8 years. I made a slow entrance due to the cost, and my moving around to stay employed in this competitive but very rewarding field.

I searched out this paper so that I could verify or refute "Snorkel Bob's" claims on Yellow Tangs life history.

I was surprised to find that the oldest fish aged was 41 years.

It appears that the science and techniques behind the study are commensurate with the best available methods to do this work. My advisor at school is an fish ageing expert, so I am somewhat qualified to know that, and my work depends on fish ages being sound for the surveys I conduct.

Just thought this would be food for thought. The abstract paragraph says it all to those that don't want to delve into the science on a Sunday morning.

Thanks to all who find this helpful/informative.:rollface:

PS- I have a Paracanthurus hepatus, a P. Euxiphops navarchus and a Foxface in that 180. P hepatus is 7 yrs old, navarchus is new to me from store and Foxface is 2 years old.

 

[Sk8r]

Very interesting. At a high-end age of 41 years, with a habitat and perhaps a diet change from early years (deeper, reef) to later years (turfed rocks and shallows) and about a 1" dimorphism (difference) between males and females, at about 7" max---it does raise some questions about how long and well we keep this species.
We get them as juvvies, and they reckon half an inch equals a one year growth. But at a 25 meter depth during early life, I'm wondering how much algae they do eat compared to say, krill, as youngsters, versus decades later in life, when turf algae seems to be the thing. Just saying the ocean is a complex world, and we sure don't know all we wish we did.

 

[gobyvin]

agreed.

agreed.

We sure don't know as much as we wish we did. It is the story of my life. That is science, for us realists, without a super ego. For obvious reasons, this species is heavily exploited but can be maintained in captivity, with space and attention to a proper diet. I am sure that many disagree, but success happens, for those that do it properly. Education is the best way to keep the impact of this hobby low and the health of the reefs up.

With eutrophication of coastal waters where reefs grow (a worldwide problem), fish that graze algae and inverts like snail, urchins and crabs are the primary line of overgrowth defense for our keystone species, corals. I shared this info to spread the effect it had on me to others that are concerned about our impact and the continuation of something we all love, the hobby.

 

[Sk8r]

People in the hobby are often very concerned that they can't immediately get these small tangs to eat nori and other greens, or that they want to gorge themselves on meaty foods. One wonders...are we asking them something they wouldn't do in the wild. At 25 meter depth for most foraging---and having not been down there, I don't know---what is there to eat but small meaty things?

 

[greenmonkey51]

From the way I read it only one person aged the otoliths. That would be far from standard procedure in aging. At minimum two people will read separately and then do it together and come to agreement. There is no median age count and tossing samples because you can't age it. As far I'm concerned the aging component of this study is junk.

 

[bmorecopper]

so I never really thought of the changing feeding pattern of fish as the get older. Most if not all of the fish I have ever bought were juveniles. Would it be more beneficial to the fish to feed them what they eat in the wild as they mature to help them live to their natural life span? Or is this not an issue?

 

[Sk8r]

If only we could figure what they eat in the wild: that's one of the big problems that we try to solve. Right now, I've got some very small fish that can only handle cyclopeeze and daphnia, and I have to break up krill with a mortar/pestle to get them to eat---and I'm sure they'll change diet as they grow. But right now you'll see them ignore food that they see as 'too big'. And the scooter only takes pods, but is showing some interest in the daphnia that comes near him. I'd rather not feed it to a marine tank, but hey, if they eat, that's a good thing, if I can get them to be a bit larger and still hungry.

 

[billsreef]

Having been to 25m (and bit deeper) in Hawaiian waters (Maui), I can tell you that there is indeed plenty of algae to graze at those depths. There also tends to be plenty of amphipods and such as well, so a reasonable amount of meaty foods to go along with that algae. One of the habitat differences mentioned is the complexity, i.e. cover for the juvies to hide in

Having spent a good bit of time aging fish myself, I'd have to agree that the aging portion of the study is weak. While it's possible for a good and well seasoned agers to produce some very accurate ring counts, it's not uncommon for two very well seasoned and qualified agers to have differing counts on a giving sample from time to time.

 

[arhyne]

Bill where exactly do you see potential error in their final models, i.e. how much error in ages given?

I'd agree that some error is always likely with tedious tasks but given the sample size is large, as it should be, I would be hesitant to use "weak" without a specific qualifier, as many readers here will not have the ability to interpret that statement.

 

[logan 12]

From the way I read it only one person aged the otoliths. That would be far from standard procedure in aging. At minimum two people will read separately and then do it together and come to agreement. There is no median age count and tossing samples because you can't age it. As far I'm concerned the aging component of this study is junk.

Like this, that is exsactly how the test is done. Two readers not one, I have done this myself on both white crappie and bluegill out of a small lake in IL. Very cool stuff, although aging otoliths is a nasty, stinky job, maybe marine fish don't smell as bad. Thinking of going into marine fisheries myself.

 

[logan 12]

While it's possible for a good and well seasoned agers to produce some very accurate ring counts, it's not uncommon for two very well seasoned and qualified agers to have differing counts on a giving sample from time to time.

Agree 100%, even an ager, take my professor who has spent many hours aging fish, mainly works with sturgeon and catfish in the wabash and mississippi. He has explaied that several times both he and another fisheries managmemer were so far off that they could not use the otolith age to determine anything not sure the precetage of error that is supposed to be between the two readers that is exceptable, will have to bust out the notes for that number.

 

[billsreef]

Bill where exactly do you see potential error in their final models, i.e. how much error in ages given?

Only one person aging leads to the probability of personal bias. That is why having 2 people read the otoliths is the gold standard

Very cool stuff, although aging otoliths is a nasty, stinky job, maybe marine fish don't smell as bad. Thinking of going into marine fisheries myself.

Other than the dissection to get those otoliths, I never considered it a stinky job. But than I've only worked with marine species.

Agree 100%, even an ager, take my professor who has spent many hours aging fish, mainly works with sturgeon and catfish in the wabash and mississippi. He has explaied that several times both he and another fisheries managmemer were so far off that they could not use the otolith age to determine anything not sure the precetage of error that is supposed to be between the two readers that is exceptable, will have to bust out the notes for that number.

Usually it's more of an issue with scales. Otoliths tend to be cleaner, but can still have rings too close and end up blurring the distinction.

 

[RGBMatt]

I searched out this paper so that I could verify or refute "Snorkel Bob's" claims on Yellow Tangs life history.

I was surprised to find that the oldest fish aged was 41 years.

This is probably true - long adult lifespans are typical of many surgeonfish species.

But, it's only part of the story. The thing is, that 41-year old fish is an extreme exception - the vast majority of yellow tangs are eaten by predators and have very short lifespans. The same researchers did a study on survivability in the wild, and estimated that only about 1% lived to reach maturity:

http://oxy.academia.edu/JeremyClais...hery_species_yellow_tang_Zebrasoma_flavescens

So, it's likely that most of the yellow tangs caught for aquariums live much longer than they would have in the wild.

 

[greenmonkey51]

Agree 100%, even an ager, take my professor who has spent many hours aging fish, mainly works with sturgeon and catfish in the wabash and mississippi. He has explaied that several times both he and another fisheries managmemer were so far off that they could not use the otolith age to determine anything not sure the precetage of error that is supposed to be between the two readers that is exceptable, will have to bust out the notes for that number.

Separate sturgeon and catfish. To age a sturgeon take 3 die toss them and you'll probably get a better answer that reading the pectoral rays. 20% agreement is at the top end of the range for sturgeon. I have looked a shovelnose sturgeon rays from the Wabash and it is not easy.

For catfish they are not as bad. Otoliths should be pretty clean up to 8 years old, past that it can get tricky. For pectoral spines unless cut correctly they can be tough. They tend not to be as good, but it is a non lethal method. For catfish I believe that 75% agreement is towards the bottom end. Just getting a little bit experience can raise that number.

Nothing about otoliths would smell really. Although most fish labs do smell like fish all the time. Its something you live with while doing research.

 

[logan 12]

We removed otoliths on over 500 fish in three hours in a class room/lab setting. Of course their was a bunch of us working up the fish, however the smell was so bad that the next class had to be cancled. The fish had been frozen for a bit of time then worked up. Trust me it was not fun for any of us. When you tear back the fishes head to get to the otoiths it stinks very much, and is just not a fishy smell at all.

My professor aged sturgeon using otoliths, his name is rob colombo.

My professor also is a scale hater, did not like aging any fish using them. Otoliths only, can't remeber how he did the catfish that was his thesis work on the wabash, between Illinois and Indiana. Two states that have very diffrent length requirments for the catfish, a very challenging fishery to manage.

 

[logan 12]

This is probably true - long adult lifespans are typical of many surgeonfish species.

But, it's only part of the story. The thing is, that 41-year old fish is an extreme exception - the vast majority of yellow tangs are eaten by predators and have very short lifespans. The same researchers did a study on survivability in the wild, and estimated that only about 1% lived to reach maturity:

http://oxy.academia.edu/JeremyClais...hery_species_yellow_tang_Zebrasoma_flavescens

So, it's likely that most of the yellow tangs caught for aquariums live much longer than they would have in the wild.

This is what I was trying to say in the It's bigger than the tang thread, Only 1% survivle. Population Ecology. Learn it love it.

Would love to post some of this research back up on that thread, but can't.