5/12/2016 – Paige Crowl

Day 3 Blog Post – 5/12/16

Well, it’s day three of the Lionfish in the Caribbean course! So far, we’ve explored some of the complications around this issue and seen how an integrated systems approach helps us to approach them better. We’ve also covered the basics of lionfish biology, how they arrived in the area, and talked about some of the damage they’re doing to the reefs. Now it’s time to dive in to fisheries and fisheries management 101! Get it? Dive in to fisheries? … Alright, no more puns.

Let’s Talk About Fish

We started off today talking about fisheries: who participates in them (harvesting and post-processing), how communities are shaped around them, and the methods and technologies used in them. Fisheries are particularly interesting to study because both a huge commercial factory ship and one person with a hook and line are part of the fisheries system.


Yep, both fishers.

On top of that, there’s such a huge diversity in fishers themselves: people can fish to feed themselves (subsistence fishers), as a cultural practice (which may also be for subsistence, but doesn’t have to be), just for the joy of fishing (recreational fishers), or to catch fish for sale (commercial fishers). Of course, these categories can overlap in a number of ways or be broken down into sub-categories as well. For example, we can look at the difference between large-scale industrial fishers and small-scale commercial fishers (sometimes called artisanal fishers). Both catch and sell fish for their livelihood, but small-scale fishers often have a deeper dependence on the fishery, because of fewer job opportunities open to them. This is important to remember when looking at the motivations of people involved in the fisheries system.

There is also a huge diversity in the equipment fishers use, depending what they’re fishing for, what they have access to, and what they can afford. Some very common fishing techniques mostly associated with the large-scale industrial fisheries are trawls and seines. A trawl net is dragged behind the boat, collecting fish as the boat travels along, and can be positioned along the bottom of the ocean floor or midwater depending what species the boat is aiming for. A seine is also dragged behind a boat, but instead of flowing out behind it like a butterfly net, it is dropped vertically into the water in a huge circle. When the boat has completely surrounded the fish it wishes to catch, the fishers simply close the circle like it’s a purse and hoist the caught fish up.

trawl netseine purse

A trawl net and a purse seine. Good thing fishers love informative diagrams.

As you can probably imagine, both of these techniques generate a lot of bycatch, which is the term for everything the fishers catch that they weren’t really aiming for. Bycatch has gotten a lot of bad press in recent years – you’ve probably heard about sea turtles getting caught in trawl nets and dolphins getting swept up in purse seines. Bycatch can also be a problem when immature or juvenile fish get caught up with the rest of the catch. After all, one of the big goals of management is to make sure the fish population persists into the future, and if the fish don’t reach maturity and reproduce before they are caught, that puts a big hole in our future plans! Fortunately, a lot of innovative fishers and scientists are developing more and more ways to prevent bycatch (i.e. turtle excluder devices, or TEDs, and monitoring techniques for dolphin-safe tuna). Nets are being made with mesh panels through which smaller fish can escape as well. These are good advances, but it’s important to remember that with these broad, sweeping fishing techniques, avoiding bycatch completely is to a large extent impossible.

turtle excluder

Rest easy, turtles. We’re looking out for you. Then maybe you can check out some good TEDTalks.

Fishing for Forever

Next we moved on to management: a hugely important issue when it comes to fish stocks! Like many other sustainability efforts, sustainable fish stock management sets out to figure out how much fishing can take place while ensuring that fishing prospect will not suffer in future years. There are a lot of complicated interlocking pieces to this, and management can be approached from numerous angles. You can regulate how much time or how many days people spend out on the water fishing in a season, you can regulate how many fish of a species can be caught in one season, or you can regulate what kind of equipment people use to fish with. These methods and more can all be explored in much greater depth, but I don’t want this blog post to go on forever! Instead, I’ll just discuss one angle from which people approach management, one which we can apply to the lionfish problem at hand: appropriate effort.


This is a Gordon-Schaefer curve! Don’t panic, it’s not as complicated as it looks. We’re simply using it to represent some of the ways a fishery can be managed. On the x-axis you can see the “Effective Fishing Effort”, which is simply how much you’re putting into a fishery: capital, time, labor, boat parts, etc. On the y-axis you can see the “Sustainable Yield or Revenue”, which is what you’re getting out of the fishery: fish, profits, etc. It makes sense that the revenue curve moves in an arc, then. You put in your money and time and leave with fish that you can sell for profit. But as fish get scarcer, it becomes more difficult to find them, and it takes more time and work to find fewer and fewer fish. At some point, you begin to put in more effort and money than the fish you’re going to catch are worth. This wastes your money and decimates the fish stocks, a big no-no all around. So there must be an ideal point at which to stop fishing! What this point is, though, depends what you’re trying to get the most of.

  • The Maximum Economic Yield (MEY): This is the point at which profits are maximized. If you put this much effort into the fishery, you get the most bang for your buck. Costs are low, the fish were pretty easy to find, and you left a good amount of them behind for next year. At this level of effort, you can maintain this level of profit year after year.
  • The Maximum Sustainable Yield (MSY): This is the point at which the catch is maximized, and enough fish were left behind to reproduce that theoretically you can catch the exact same amount next year. This sounds great, right? Of course, though we can make well-informed hypotheses based on history and fish biology as to what level of effort (and number of fish caught) this point is, we can never be 100% sure. There’s always the chance that we overestimate or underestimate the breeding capability of a species and end up with a lot more or fewer than we expected to in a few years. A small mistake can ruin a fishery or decimate a stock to the point in which it takes decades to recover, or never manages to. But if you set a good catch limit, you can get a lot of fish moving out to hungry consumers in a very sustainable way, and protect your valuable fish stocks for the future. As you might be able to guess, most fisheries today are managed with the goal of MSY in mind.
  • Open-Access Equilibrium: This is the point at which the fishing effort is maximized, maximizing fishing employment. Since revenues equal costs, there is no profit being generated on the fishery as a whole (this is not to say that individual fishers wouldn’t make money, by the way).


The Trouble with Lionfish

So how does all this fit in with the lionfish issue plaguing the Caribbean today? Well, quite well, actually. Establishing a fishery could be a great solution to the massive lionfish invasion we’re facing.

capt kirk

If you think Captain Kirk looks miffed now, just wait until he sees the reproductive nightmare behind him.

As I’m sure you’ll recall from yesterday’s post, lionfish have multiplied at an astounding rate in the Caribbean. A single fish can reproduce every 3-4 days! If this doesn’t terrify and disturb you, take a second and think about it again. These fast-replicating fish have spread from South Florida to almost every island in the Caribbean in just 30 years.

game of thronesmap

Lionfish: more terrifying than White Walkers? You decide.

Remember that idea of Maximum Sustainable Yield we discussed? We were assuming that we wanted to maintain a stock for fishers to draw from well into the future, and when that limit was accidentally or deliberately crossed, it could spell disaster for the fishery. But the one advantage that lionfish have over other fish here is that they seem to reproduce constantly. It seems that we can draw from this stock a great deal before we will come even close to exhausting it. But the good news is that even if we do manage to exhaust the lionfish resource in the Caribbean, the problem is solved anyway! Establishing a fishery could be the solution we’re looking for. If nothing else, it’s a good way to put a dent in their population.


Smeagol’s got the right idea – catch and eat that juicy sweet lionfish!


Oh, maybe not quite like that, Smeagol. We were thinking more like this:

tasty lionfish

Yum yum!

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