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Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

Oct 25

Written by: Ret Talbot
10/25/2011 5:54 PM  RssIcon

I had the chance to interview Dr. William Walsh last week while I was on the Big Island researching the passage of Resolution 130 for MASNA and CORAL Magazine. During our time together, Walsh shared a lot of data with me. In most cases, it was the same data he shared with the Hawai‘i County Council who recently voted in favor of a Resolution seeking a statewide ban on marine aquarium collection. The data doesn't appear to support the Resolution’s claim of “devastation,” at least not in a traditional fisheries management sense. This blog entry looks specifically at the most current data on one of the most talked-about species in West Hawai‘i—the yellow tang.

Dr. William Walsh

While some anti-trade activists have alluded to “other data” contradicting the data put forth by the state aquatic biologist Dr. William Walsh, I learned in my interview last Thursday with County Council Member Brenda Ford, who authored 130, that she believes Walsh’s data is sufficient to warrant a statewide ban. 

I was fortunate to have the opportunity to spend the better part of a day with Walsh while I was in Hawai‘i researching the story for MASNA and Coral Magazine. An edited (for space) version of my interview with Walsh will published in the Nov/Dec issue of Coral (the full interview will be available online), but I’d like to share a few highlights from the interview here.

An Apparent Flip-Flop on Management of the Marine Aquarium Fishery in Hawai‘i

Despite the apparent flip-flop of the Hawai‘i County Council from supporting the fishery management tools proposed last September and opposing a ban late this September to voting in favor of a ban in early October 2011, Walsh told me “nothing fundamental has changed since last year.” If anything, we know more about the fishery today, and there is more data to support Walsh’s assertion the fishery is moving in the direction of one that is well managed and sustainable.

So how is it Council Member Brenda Ford, the author of Resolution 130, claims Walsh’s data shows “devastation” necessitating a statewide ban on aquarium collection? The answer, I think, is quite simple. As I reported previously, many opponents of the aquarium fishery refuse to call the marine aquarium fishery a fishery, and Ford is no exception. As such, for Ford and others like Robert Wintner (aka Snorkel Bob), the commonly accepted litmus test for fishery sustainability (or lack thereof) does not apply. While I believe Ford’s assertion of devastation is worth exploring (the reefs of Hawai’i certainly are being heavily impacted by a wide range of anthropogenic stressors), it does not appear to be an assertion about sustainability using traditional fisheries management language.

A Fishery is a Fishery

Using the standard definition of a fishery widely accepted by fisheries biologists and others who manage and create legislation to manage fisheries, a marine aquarium fishery is really no different from a food fishery in terms of how it is defined and how sustainability is determined. The Magnuson-Stevens Fishery Conservation and Management Act, the primary law governing marine fisheries management in the United States (primarily in federal waters), asserts a fishery is “one or more stocks of fish which can be treated as a unit for purposes of conservation and management and which are identified on the basis of geographical, scientific, technical, recreational, and economic characteristic.” Likewise, according to the Magnuson-Stevens Act, “the term fishing means the catching, taking, or harvesting of fish.” Hawaii Administrative Rule 13-74 likewise defines fishing as

catching, taking, or harvesting, or attempting to catch, take, or harvest, aquatic life. The use of a pole, line, hook, net, trap, spear, or other gear which is designed to catch, take, or harvest aquatic life, by any person who is in he water, or in a vessel on the water, or on or about the shore where aquatic life can be caught…

If we can agree the marine aquarium fishery is indeed a fishery (and that marine aquarium collectors are indeed fishers), then we can get down to brass tacks and ask the real question: Is the marine aquarium trade in West Hawai‘i being fished sustainably? 

The Magnuson-Stevens Act, states “the terms ‘overfishing’ and ‘overfished’ mean a rate or level of fishing mortality that jeopardizes the capacity of a fishery to produce the maximum sustainable yield on a continuing basis.” Is that what is happening on the reefs of Hawai‘i? Here is some data that may help us to answer that question. Everything below in quotation marks is a direct quotation from Walsh based on the data collected by DAR staff biologists and others along the Big Island’s Kona Coast. 

“In 2010 over 430,000 animals were collected on West Hawai‘i reefs with yellow tang comprising 81 percent of the catch,” says Walsh. “From 1999, when we began WHAP [the West Hawai‘i Aquarium Project], to 2010 the number of collected yellow tang increased from 165,254 to 311,480—an increase of about 88 percent.”

“From 1999 to 2010 the yellow tang population of mostly immature fish in the 30’-60’ depth range in West Hawai‘i increased from an estimated 2,236,858 to 2,573,909, an increase of 337,050 or slightly more than 15 percent. [For reasons explained in the full interview in Coral Magazine, that 15 percent statistic likely underestimates the West Hawai‘i yellow tang population increase since 1999.].” 

“Over this same time frame the number of collected yellow tangs has increased 88 percent. So while yellow tang take has increased along the coast over the past decade, the total abundance of yellow tangs has also increased.”

That Surely Doesn’t Look Like Devastation

That surely doesn’t look like devastation—in fact, it might even look like categorical sustainability everyone could embrace…except for the fact the data, averaged over the last three years, shows 68-percent less abundance of yellow tang in open areas compared to FRAs. Walsh told me this number concerns him, and opponents of the trade use this abundance differential statistic frequently to argue management is not working.

According to the data, the yellow tang is one of only six species on the proposed white list to show a consistently lower abundance in open areas than closed areas. Unlike the other five species, which show more variability, from 1999 to 2008 the disparity between the abundance of yellow tang in open areas and FRAs generally widened. Following a good recruitment year (and possibly recession impacts) the disparity has started to narrow in 2009 and 2010. 

I asked Walsh what he thought of the oft-cited disparity statistic, which is frequently used by opponents of the marine aquarium fishery. While Walsh says this number does concern him, and he says he wants to reduce it, he also points out the following:

“It is important to note that a large part of the difference in yellow tang abundance between the FRAs and the open areas relates to the fact that yellow tang abundance has increased so much in the FRAs—it’s up 71 percent since 1999. The protected areas are working very well. During this same time period the open areas have decreased by 19 percent [and] this is where the fishing—at increasing levels—occurs.” 

“Even if there was no decline in open area yellow tang abundance,” Walsh continues, “the difference between those areas and the FRAs would be substantial just due to the increased numbers of fish in the protected FRAs. Overall, on West Hawai‘i reefs as a whole, yellow tang populations have increased by 15 percent in the 30’-60’ depths since 1999.”

Other Species of Concern

For the record, I want to be very clear there are other targeted species to consider besides the yellow tang, but the yellow tang is the vast majority of the catch and it is the species that gets a lot of the airtime, so it’s a good place to start. In a future post, I’ll share some of the data showing downward trends in a few of the species currently targeted by the marine aquarium fishery on the Kona Coast of the Big Island. I assume these are the species, in addition to the yellow tang, about which Council Member Ford was speaking. I’ll also let you know what Walsh shared with me about the proposed management for those species. 

Spoiler alert: While there are indeed some downward trends in Walsh’s data, there is nothing I have seen leading me to conclude the fishery cannot be managed in a sustainable manner if we use science-based management and the widely accepted language of fisheries management.  




Copyright ©2011

6 comment(s) so far...


Re: Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

1. Though the fish taken by the aquarium collectors are in State waters and not subject to federal fisheries, but if they were they would be considered unmanaged and unregulated: The Magnuson-Stevens Act requires the management units to be species or taxonomic groups, with a maximum sustained yield calculated for each. “Unless identified with a specific maximum sustained yield, the resource will not be considered to be regulated or managed.” Of course the Magnuson-Stevens Act does not adequately address fishing on coral reefs, since a species-by-species approach is ineffective for complex coral reef ecosystems.

2. When the no-take areas were established and long term monitoring began, the top 10 targeted species had already been reduced by an average of 59% in West Hawaii (yellow tangs had been collected to commercial collapse on Oahu). Since 1999, 7 of the top 10 species are still declining within the no-take areas, at least 9 of the top 30 species have declined overall (collected & protected) since 1999. Since the 1970's when collected began in earnest in West Hawaii, bluelined butterflyfish, hawaiian turkeyfish, bandit angelfish, thornback cowfish are among those once commonly sighted and now rarely seen.

3. The 73% average gap between protected and collected areas is widening because of how many are being taken not because the protected population is growing. In fact, the overall trend in long / med. term protected AND collected areas has been downward since about 2004. It can easily be argued that the reason for this is because of the number taken by the trade each year. Of course, Matt and Ret will say "that's not why they're declining" and of course Walsh will continue to use the increased numbers from the FRA's to try and offset the decreases but very few are buying it.

4. Only those with vested interests in the trade, whether financial or emotional, are ok with what the aquarium trade is doing to Hawaii's wildlife populations and reefs.

By Rene Umberger on   10/30/2011 9:52 AM

Re: 19 percent decline

I just want to point out, I've been emailing with Ret about this 19% figure that Walsh is quoted with, because another document put out by DAR reports only a 5% decrease in open area tang populations ( ). Obviously a 5% decline in open area population is far less concerning than 19 decline, and it got me wondering why there's a disparity in between these two numbers. I.e. are these percentages over different time periods? Is one the number for tangs of all sizes, and the other the number for only juvenile tangs? To me, the disparity between closed and open areas is a semi-moot point, it's the hard population numbers that are easier for the layperson to understand. A 68% disparity sounds huge, when in fact it is largely representative of a massive increase in population in the FRAs. To help further explain what that disparity figure means - year one, we start with 100 fish in the FAR, and 100 fish in an open area. The disparity is 0%. 10 years later, we have 200 fish in the FRA, and 100 fish in the open area. That's a 100% disparity. I think this is why people who are pushing to close the fishery may be latching onto figures like the disparity figure cited sounds huge, sounds scary, and if you really don't dig into what it means (and realize it's simply a ratio, not a measure of population itself), it can be used to misrepresent what is really going on.

By Matt Pedersen on   10/27/2011 11:17 AM

Re: Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

Thanks for the comment, Matt. I think I'll address your comment fully in a future blog entry, but the short answer is this:

The 5% figure stated in the FishLife piece is outdated, although the article's premise--that this should be viewed as a success story--remains the same. This is a dynamic ecosystem heavily influenced by recruitment rates and more. The numbers from year-to-year can vary widely. The 5% was a valid figure in 2007 or 2008 when DAR requested the data for the article. When comparing 1999/2000 data to 2006/2007 data, you get 5% decrease in open areas and the 95% increase in the FRAs. The comparison between 1999 and 2010 yields the 19%. This, in and of itself, is NOT cause for concern. There is a lot of year-to-year variability in recruitment resulting in corresponding year-to-year abundance variability in all the survey areas. The percent change in abundance from any year (1999 in the above examples) to the most recent year will almost invariably be different from one year to the next.

Monitoring the difference in abundance between open areas and closed areas is very important, as it one of the most powerful ways to measure whether or not the management tools in place are working. Without this data, you would not be able to have such a positive article like the FishLife piece proclaiming that "[the yellow tang story] has the potential to be a success story that people can apply in other parts of the world."

Of course as you point out, Matt, we need to keep the big picture in mind, and the big picture is this: From a fisheries standpoint, management is working given the current pressure on the yellow tang stock because there is virtually no pressure on the reproductive stock, and the spawning potential ratio is near 100%. That's the take home point here when it comes to science-based fisheries management.

By Ret Talbot on   10/28/2011 3:11 PM

Re: Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

I’d like to take the opportunity to thank Rene for the ongoing dialog and her willingness to look at the data available to us as we formulate our opinions on this important issue. In the interest of continuing the conversation, I’ll give a few thoughts here, and then I’ll follow-up with more detailed blog entry so the discussion is not lost to the comments field.

Regarding the Magnuson-Stevens Act, I agree it does not apply in a direct management sense to the vast majority of the marine aquarium fishery in Hawai’i. Even if it did apply, there are many unresolved issues with the Magnuson-Stevens Act. I’ve written about these issues in the past in terms of food fisheries, but this isn’t really the venue for those discussions. The reason I brought up the Magnuson-Stevens Act is because it gives a commonly accepted definition for a fishery. As Rene knows, there are many people who supported Resolution 130 (and other anti-trade initiatives) who refuse to talk about the marine aquarium fishery as a fishery. In citing the Magnuson-Stevens Act, I am simply trying to propose a linguistic starting point from which we can move forward. I’m happy to bring other definitions into play, but by every commonly accepted definition with which I am familiar, the marine aquarium fishery in Hawai’i is a fishery.

Regarding Rene’s 59% figure for the top 10 species, that does not square with the data at which I am looking. I’d very much like to see the citation for that number. In terms of the bluelined butterflyfish, Hawaiian turkefish, bandit angelfish, and thornback cowfish (I would also add the teardrop butterflyfish to that list), I agree these are indeed species of serious concern. My understanding is evidence of significant change in abundance on West Hawai’i reefs for these species was, at least in part, what lead to the creation of the Species of Special Concern Subcommittee (created by the West Hawai’i Fisheries Council in 2006). As a result of that committee's work, as well as the work of many others, all of these species will be off limits to aquarium collection once the White List goes into effect in early 2012, correct? This is science-based management, is it not?

On the 73% statistic (“average gap between protected and collected areas”), I’d love to know more about the source for that statistic. It is a statistic I have seen used a lot, but I have not seen the citation unless the 73% is being used out of context. I’d also like to see the citation for the claim that the overall trend has been downward since 2004. As I wrote, the numbers I have seen show only six species on the proposed white list with consistently lower abundance in open areas than in closed areas.

Once again, I’m glad we can have an open dialog looking at the data as opposed to relying on emotion and anecdote. I don’t mean to suggest emotion and anecdote are irrelevant; I’m simply suggesting data is what will help us answer the question of whether or not the marine aquarium fishery in Hawai’i is sustainable in terms of the commonly understood definition of the term.

By Ret Talbot on   11/2/2011 11:15 AM

Re: Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

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Re: Increasing Yellow Tang Abundance in West Hawai‘i and Resolution 130's Relationship with the Data

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