When Ken retired from his electronics engineering career five years ago, he saw a lot more fishing in his future but it didn’t work out that way. Today, he can probably be best described as a full-time volunteer conservationist who occasionally goes fishing. Tomorrow, he told me he plans to start doing something about the “occasionally” part
Guessing at Striped Bass Abundance in Maryland. Not an Exact Science
In my simple mind, fisheries management relies on three basic data points:
1. How many fish there are.
2. How many fish will die.
3. How many fish will be left.
That’s it – everything else is derived from
these three concepts. We can’t count fish that swim around and wander over thousands of miles of water so No. 1 is a statistical crap shoot sometimes, but not always, based on actual survey data input to an abundance model. No. 2 is made up of fishing mortality and natural mortality but only legal fishing mortality could be directly measured while natural mortality is another roll of the dice. If you knew the first two, simple subtraction gives you the last one.
I’m probably not smart enough to understand the statistical parts so I went right to the “how many die” part because it seemed easier. Annually, MD reports to the Atlantic States Marine Fisheries Commission (ASMFC) how many fish were caught so ASMFC can decide whether MD stayed within their quota. I went directly to the 2009 Compliance Report. (The 2010 report wasn’t ready last summer when I started my quest.)
Before I got to the real meaty parts, I derived the following conclusions from the report:
1. The commercial fishery was very close to its quota.
2. The recreational fishery exceeded its quota by almost one million pounds.
3. The average weight of a commercial fish was 3.7 pounds.
4. The average weight of a recreational fish was 9 pounds.
The commercial fishery being close to its quota, on paper, is pretty much guaranteed by the way MD manages the fishery. DNR issues a tag per fish until the total REPORTED harvest approaches the magic number and then shuts down the fishery. Everyone knows that widespread fraudulent under-reporting of weights is a threat to the validity of this approach so, while the report says they were close, the only fact you can count on is that they were actually over their quota – we just don’t know by how much.
The recreational fishery being over quota was alarming and I wondered how that happened and why no one raised a flag. So, I started looking more closely at the numbers of fish and total weights for the two fisheries which failed the “sniff” test because:
1. Both groups exploit the same population of fish.
2. The commercial slot limit and seasons give them a better shot at larger fish.
3. The recreational average should have been smaller, not 2.4 times larger.
The only logical conclusions are:
1. The commercial catch is under-reported.
2. The recreational catch is over-reported.
3. The errors are probably significant.
4. Even ASMFC doesn’t believe the recreational data.
5. No one knows how many fish were caught in MD.
So, we start with a “guess” (ASMFC prefers “estimate”) about how many fish there are and subtract the following to arrive at an estimate of abundance:
1. The estimated harvest that is obviously wrong.
2. An assumed constant natural mortality that is questionable.
3. An estimate of how many recreational discards died.
4. No allowance for commercial dead discards or poaching.
Fortunately, there are other indicators of abundance and the ASMFC Striped Bass Technical Committee has admitted that the actual abundance is lower than that obtained from the assessment models. Among the potential sources of errors:
1. Under-reporting of harvest.
2. Poaching levels that can no longer be ignored.
3. Increased natural mortality from micobacteriosis.
My understanding of this subject got a huge boost when DNR publicly admitted that the commercial fishery was not sustainable due to under-reporting and poaching. Fisheries staff said they could no longer feel confident that they were managing the fishery within the established quotas. Really? Once you admit that your harvest may be over your quota, don’t you have to accept at least the remote possibility that the overage could be significant? Is “no longer feeling confident” the same as “doubting?” How about this; “We are definitely over our quota and we don’t have a clue about how far.”
And what do we know about poaching in MD?
1. Some fishermen never stopped using anchored gill nets when they were banned.
2. We can’t be sure we found all the abandoned nets and rotten fish last year.
3. No one was ever prosecuted for illegal gillnets last year.
4. There is a market for untagged, unchecked fish from MD even during the closed season.
5. Mis-tagging of fish set a new standard for corruption in 2011.
It is probably not wise to brag that we aren’t fishing over our quota just because ASMFC, using the data we knew was wrong, said so. We can’t very well hide behind the fraudulent data we provided while proclaiming that we are “no longer confident” that it is right. Also, I would probably shelve that “Best Managed Fishery on the Atlantic Coast” comment until I got some of this under control.
Definitely not an exact science.
Ken Hastings
More fresh new served up later this week. Until then, get out there and do some fishing. The striped bass bite has been on fire off of Virginia's Eastern Shore and the Bluefin Tuna bite red hot off Virginia Beach. Check the Virgina Fishing Forum for all the Fishing Reports and fishing pictures.
Brandon
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