On the Ubiquitous Striped Bass “Slot Limit”

Why such a proposal isn’t the solution many people think it is

Photo by Capt. John McMurray

Photo by Capt. John McMurray

If you are a regular reader of this blog, you are probably aware that I’ve touched on the issue of slot limits for striped bass a few times. In case you didn’t already know, a “slot limit” implies a keeper-size fish between certain parameters (e.g. 24 to 28 inches). The idea is to limit mortality on the large, fecund females that theoretically contribute more to reproduction.

It certainly sounds reasonable, if not outwardly beneficial to both anglers and the striped bass stock. But in the real world, it doesn’t really work out that way. I’ll get to why in a second, but perhaps we need to frame the discussion first.

Truthfully, I wasn’t really planning on writing about slot limits until after the Atlantic States Marine Fisheries Commission (ASMFC) Striped Bass Board had voted out two addenda for public comment, which will hopefully happen in the second week of May. But, my intended subject fell though at the last minute, so here we are. Getting back to the addenda, the first one covers the adoption of the new, more conservative fishing mortality reference points recommended by a benchmark stock assessment that was completed last year. (For some background on this and to gain a better understanding of such reference points, I suggest reading my post ASMFC moves on striped bass). The second addendum will propose a range of management measures that would reduce fishing mortality and get us to the new mortality target suggested in the benchmark stock assessment, with an implementation date of January 2015. So, for the purpose of this blog, the real question is, “What will get us the required fishing mortality reduction?”

It’s pretty clear to me that a slot limit, at least on its own, won’t. Generally, slot limits increase fishing mortality; they don’t decrease it. That’s because smaller fish are of course dumber, easier to find and easier to catch. If you allow people to kill smaller fish, then fishing mortality goes up. That’s just common sense. It’s also pretty darn obvious, to me anyway, that those big fish we all seem to want to protect won’t get to be big fish if we focus mortality on the younger, smaller fish. I’m not sure why, but very few people seem to be willing to acknowledge that you don’t get big breeders to protect if you kill them off young.

Perhaps the larger issue is that you end up killing a lot of fish that have yet to spawn with a small slot. The current 28 inch coastal size limit theoretically allows around 50 percent of the fish to spawn before reaching keeper size. You don’t get to 100 percent until you’re in the 34-36 inch range (which is just one of the reasons why I believe having a larger size limit would do much more for the striped bass stock than a slot limit).That’s fisheries management 101. Let ’em spawn at least once before we have at ’em.

Another important consideration is that a slot limit would absolutely focus mortality on some very specific year-classes. In the case of striped bass, as I’ve discussed in other posts, we’ve got a lot of weak year-classes coming along the pike. Do we really want to throw most of the fishing mortality on those substandard year classes? That sort of focused effort could diminish an already weak age-class, and, given the current pressure (everyone and their mother these days is a striped bass angler), it’s not unreasonable to assume that a good portion of those fish would be gone before reaching spawning age. An appropriate size limit allows you to spread mortality out over a much broader swath of the population. That makes sense to me, because from a biological perspective what you want really is diversity, or, in other words, a good stratification or a lot of different year-classes.

With all this said, I suppose you could put a slot in place that changed every year so you wouldn’t put excessive pressure on a weak year-class. In other words, there would need to be an annual slot management assessment based on the success or failure of the young-of-the-year results. The problem is that this sort of managing would take major resources (aka crazy money), not to mention time. Any such slot changes would have to go thought the required analysis and rule making process, which generally takes years. I’m not sure how that would work. But the point is that it just wouldn’t be practical, nor, IMO, possible the way the management system is currently set up. And regardless, you still are killing fish before they have spawned, which just isn’t right in my mind.

Photo by Capt. John McMurray

Photo by Capt. John McMurray

But getting back on point, given what I’ve said here, it should be no surprise that in the few cases where striped bass slots limits have been implemented, there’s been a tradeoff – a “conservation penalty” – because killing a little fish has a greater impact than killing an older fish that has spawned one or more times.

If you look at New York’s commercial regulations, only fish in a 24-36 inch slot may be killed, which I believe was adopted because of PCB contamination concerns. As a result, New York’s quota was cut by (I think) around 30 percent to compensate for the slot’s greater impact on striped bass mortality. Maine set its slot limit absurdly low at 22 to 26 inches (or one fish above 40 inches.) As a result, Maine was required to go to a one fish bag limit in order for the slot to have “conservation equivalency” to the coastal regulation of two fish at 28 inches.

Yes, I get the whole larger-fish-produce-more-eggs argument. Of course that’s true, and there’s certainly some benefit there. Yet aside from my prior point that fish have to live to be older females first, there are other assumptions/flaws in this argument.

First, it’s not entirely correct to assume that more eggs equal more fish. It’s my understanding that, unless the spawning-stock-biomass has dropped so low that the number of eggs is very small, there isn’t all that much of correlation between spawning stock biomass and recruitment. It’s more of a matter of competition and relative survival. In other words, if you have a relatively small spawning stock biomass and not that many fry hatch, there is little competition among the fry; there’s plenty of food and little need to travel far from shelter/cover and feeding areas, which means that a relatively small proportion of the year-class is killed. On the other hand, a big spawn results in a lot of competition, a lot of fish that need to spend more time in open water in order to get adequate food, and far greater losses. As I’ve mentioned a few times in this forum, variation in year-classes probably has more to do with shifting environmental conditions than with the size of the spawning-stock-biomass (e.g., Atlantic Multidecadal Oscillation).

As I mentioned above, what you really want here isn’t just a lot of “big old females” (BOFs) but stratification/diversity – in other words, plenty of age-classes that make it to spawning age. So if you have several years of spawning failure, as we saw in the ’70s and ’80s, you have at least some big, fecund older fish that can produce solid year-classes once the conditions get better again.

Make sense? I know, not really. It does seem counterintuitive, but the above is pretty much accepted as fact among the scientists who work on this sort of thing.

I guess we’ve gotta cover the issue of release mortality on BOFs here, also, because in my mind it’s a pretty important consideration. But before even going there, I can’t help but think that once we got down to an actual proposal, there’d be little support from the party/charter fleet. Their clients generally wanna kill big things. I can’t imagine the Montauk fleet – or the Captree guys, for that matter – agreeing to throw back all those 40-plus-inch pigs they catch. The reality is that striped bass for the most part are targeted for their trophy potential. I don’t think that it’s really a coincidence that most of the support for a slot limit appears to be coming from the fly/light-tackle folks, which as a group typically doesn’t spend a majority of its time searching for larger bass. The great majority of striped bass fishermen, however, do target larger fish. For one, that probably means little support for a slot limit. But if such a proposal were to succeed, it likely would mean a lot of discard mortality.

It’s pretty well known at this point that release mortality becomes greater as the size of the fish increases. And don’t forget: Even if you are releasing that fish, you gotta grab it by the lip or hold it up with one of those goddamn Boga grips while likely tearing up the insides of the fish to get your hero shot. Yeah, I’m sometimes guilty of that, also, so maybe I shouldn’t be throwing stones.

Really though, it’s probably better to let people keep a bleeding or burned-out bass rather than tossing them back, belly-up. Better that such mortality be captured unless you were to have mandatory circle hooks for bait (which is incredibly unlikely and even if it did happen would be virtually unenforceable) and a law such as Florida has for tarpon that requires that large fish be released without moving them from the water (again, extremely unlikely). The point is that discard mortality on those fish that exceed the upper slot limit would likely be pretty high.

I’ve tried to explain all this to anyone who suggests a slot limit is the answer to all the striped bass problems. But inevitably I hear the question, “Well, why does it work so well with red drum, then?” Admittedly, I’m not terribly familiar with that fishery, but I do know that there are real physical differences as well as distinct dissimilarities in the ways the two species are managed.

Photo by Capt. John McMurray

Photo by Capt. John McMurray

As noted, striped bass are managed on the basis of biomass and fishing mortality reference points, whereas red drum are managed for “escapement” in which 40 percent of the fish ideally “escape” into the spawning stock biomass. Thus, anything bigger than the high end of the slot helps fill the escapement objective. This seems to work for red drum, because, for one, it seems like the bulk of red drum fishermen seek “puppy drum” that fit in the slot, both because the big fish are not as readily available and because big red drum generally aren’t kept for food. In addition, a red drum typically is harder to kill and seems to be able to survive longer out of the water. Red drum also don’t seem to be gut-hooked as often as bass because they have an underslung mouth used to pick up a bait, rather than a big, forward-facing mouth used to catch fish by rapidly sucking in large quantities of water.

Those considerations aside, I suppose if you really wanted to make a slot limit for bass work, you could go back to square one and revamp the entire striped bass management plan and manage on the basis of “escapement,” but I don’t think it would be worth all that effort. First, the current Fisheries Management Plan (FMP) appears to be working well when managers take the required precautionary steps before it’s too late (although that hasn’t been the case lately, but that’s neither here nor there for the purpose of this discussion). Also, people still will largely target the BOFs, even if they have to toss them back, and we still likely would have a huge discard mortality problem.

I feel like I’ve got to mention snook here, too, as they are also managed with a slot limit. Again I’m not terribly familiar with the biology or management of that species, but from what I understand they are in a different league altogether. You’re dealing with a data-poor, much-in-demand gamefish that is vulnerable to massive cold-induced mortality events. I think that a slot is in place for them simply because any minimum size that would adequately constrain harvest wouldn’t allow guides’ customers to take any fish home. Like the Maine striped bass slot, it is largely driven by a desire to harvest and not by conservation considerations. In other words, it doesn’t necessarily constrain harvest or benefit the stock at all.

As usual, this is long-winded. My overarching point is that, unless I’m missing something, slot limits don’t really accomplish anything save allowing people to kill dinks. I still fail to understand why so many people are fascinated with the idea, some seeming to be married to it even after being given the facts. Sure, the small ones taste better, but do we really want to take such a risk? I don’t think that we do.

All this said, I have seen no real technical analysis of what effect a slot limit would have on the reference points. I suspect we will see such analysis in the aforementioned addendum, and I may have to eat these words. But, if they can get fishing mortality down to the appropriate level while implementing some sort of slot, then I suppose it would be OK. But I’d have a lot of questions.

Honestly, getting fishing mortality down to a level that will result in on-the-water striped bass conservation is all I’m concerned about. If we can do that with a slot limit, fine, but I don’t know how we can without serious risk and tradeoffs.

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After obtaining an undergraduate degree in Political Science from Loyola College in Maryland, Captain John McMurray served in the US Coast Guard for four years as a small-boat coxswain and marine-fisheries law enforcement officer. He was then recruited to become the first Executive Director of the Coastal Conservation Association New York. He is currently the Director of Grants Programs at the Norcross Wildlife Foundation in New York. He is the owner and primary operator of “One More Cast” Charters. John is a well known and well published outdoor writer, specializing in fisheries conservation issues. In 2006 John was awarded the Coastal Conservation Association New York Friend of Fisheries Conservation Award.

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One comment on “On the Ubiquitous Striped Bass “Slot Limit”
  1. avatar WildBill says:

    As an ecologist I have to say that population dynamics are certainly not a “one size fits all” proposition. That being said I’ve never liked slot limits. The main reason is that they are largely based on politics and not on science. The compromise is to keep fisherman happy while not severely altering populations. When I wear my fisherman hat I’m aware that some people, in fact many, like to keep fish to eat. But if the issue is to have a long term viable population of striped bass than the focus should be on conservation or the alternative will be no fish to eat at all.

    Allowing all fish to reach 34 inches before they can be kept would almost certainly be a better way to increase populations so they are more resistant to other factors that make the numbers vary significantly every few years. Yes there are problems that nature seems to sort out regarding large numbers of juveniles that eat voraciously but all in all I believe a larger, more sustainable population can be achieved by making the “keeper” size at least 34 inches.

    Even with eliminating slot limits and going with a larger keeper size there will still be variability in decade to decade population dynamics. But the overall numbers should be better for striped bass.

    It appears that higher numbers of striped bass may lessen other fish populations. For instance higher striped bass populations seem to correlate well with lower shad populations. Predatory behavior by bass on shad is a likely candidate for this result.

    Complicated stuff, no doubt. Science has the capability of eventually sorting all this out. We just have to keep the politics out of the decision making.

2 Pings/Trackbacks for "On the Ubiquitous Striped Bass “Slot Limit”"
  1. […] all that much talk of the viable alternatives themselves save the “slot limit” option, which I wrote about a few weeks ago. Even then it seemed like the discussion was more about how to game such a limit to maximize […]

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