From: jokim@jarthur.claremont.edu (John H. Kim)
Subject: Re: New Jersey Tuna Fishing
Organization: Harvey Mudd College, Claremont, CA 91711
Date: Tue, 29 Sep 1992 17:30:43 GMT

levesque@wahoo.enet.dec.com (Mark Levesque) writes:
> Peter Cherasia (cherasia@viper.bear.com) wrote:

>>The problem lies in the fact that the fish take a long time to reach 
>>maturity and their breeding population keeps dipping lower and lower every 
>>year. 

> Yes, it is a problem that the fish take a long time to mature. People
>catching and keeping juvenile fish exacerbates this problem by ensuring
>that a smaller population will get an opportunity to reach maturity in
>the first place.

> These aren't bluefish. It's not like the fish you kept had reached their
>potential.  You stopped them before they even got started. I'd be ashamed
>to say that I kept a 15 pound bluefin, just as I'd be ashamed to say I
>kept an 8" striped bass.

I agree with the spirit of your posting, but I don't think this is as
simple as you make it out to be.

With a species which produces few offspring, of which a large portion
reach maturity, you want to protect the fish from birth til a few years
after maturity.  If I'm not mistaken, striped bass fall into this category.

With a species which produces millions of offspring per fish like tuna,
of which a small portion reach maturity and are slow to mature, you want
to concentrate your protection on the mature breeders.  Taking a single
200 lb tuna will make a much bigger dent in the breeding capacity of the
species than taking ten 20 lb tuna.  That's because chances are slim
that even one of those 20 pounders would have reached maturity (I'm not
sure on the exact mortality figures) much less 200 lbs.

If this isn't clear, draw two graphs.  On the Y axis, plot the number
of fish.  On the X axis, plot the age of the fish.

With a species like tuna, the population line will be in the billions
if not trillions near zero years, running down to a few tens of thousands
at 8 years or so (around 200 lbs in weight).  If you were to kill a
hundred million newborns, you would hardly make a dent in the population
by the time the remaining newborns reach 200 lbs.  (Just what is the
mature weight for bluefin anyway?  It's around 60 lbs for yellowfin.)

With bass, you can probably count the number of eggs if you catch a
mature female (I've only caught one largemouth in my life so I'm basing
this on other freshwater fish).  Their population doesn't decline as much
from newborn to maturity.  I'd speculate a large lake would have tens of
thousands of mature bass.  Kill a hundred million of their offspring at
once and you've dealt a serious blow to the population.

For good fisheries management, you want to concentrate your catch on
what harms the population least, yet produces the greatest tonnage of
fish (add a third Z axis which equals number of fish times weight).
That point is going to be a smaller fish for tuna (relative to a mature
fish) than for bass.  I'll even go so far as to speculate that point
is probably right around 15-30 pounds for bluefin (1-2 years old).
Incidently, this is part of the reason why slot limits are in use for
some species.

> 1. No bluefin taken in the gulf of Mexico
> 2. Minimum size of 200 lbs for all bluefin- violations may cause seizure of
>boat and all equipment.
> 3. 1 fish maximum per boat per day/ 2 fish max per season
> 4. No purse seiner licenses. No harpoon licenses. Only "general" licenses.
> 5. Export fee for giant bluefin tuna = 100% of dock price; money earmarked
>for use in reestablishing the fishery

The thing is the major problem has always been lack of enforcement
rather than lax restrictions.  You're going to have a tough time just
inspecting 0.1% of the boats that go bluefin fishing each day, much less
enforce a 2 fish/season limit.
-- 
John H. Kim                 | (This space to be filled when I
jokim@jarthur.claremont.edu | think of something very clever 
uunet!jarthur!jokim         | to use as a disclaimer)
Newsgroups: rec.outdoors.fishing