Okay, FIRST- methods and technologies have improved since then, so while today it's easy to get the data from much fewer specimens, back then it wasn't.
SECOND- This didn't happen all at once; these specimens were taken over multiple years, and the fish were never wiped out all at once until well after this study was finished, and only then by other parties.
THIRD- In case ya'll missed it, these fish are hard to find and harder to reach. Going to the same spot over and over again was likely a matter of convenience as much as keeping the samples from the same population instead of risking data contamination from having possibly differentiated characteristics from disparate populations ruin the meaning of any data collected.
FOURTH- Knowledge isn't free. Sometimes the price is high. For example, pretty much everything we know about human embryology was learned either directly by, or derived from, the data collected by Josef Mengele's abominable experiments on pregnant jews in WW2. Disgusting, yes, but thousands of people owe their lives to it today. Don't get me wrong; THAT really WAS a disgrace to science, but it's a fun little tidbit I like to mention for the fun of the revulsion it causes. Hey, if you want to compare or even equate collecting 800 minnows to some sort of holocaust, then now you can.
It doesn't seem quite as bad now, does it?
Finally, it's not very feasible for a professor and a bunch of transient students to set up and maintain an ongoing breeding program for a fish, especially a fish with a non-breeding reputation, even in an AG & Tech school like Auburn. The universities aren't keen on devoting so much space and resources on something they don't see a really good reason for pursuing. Heck, sometimes it's hard enough to get a fishtank set up in the hallway. I once tried to donate one to Troy and they turned it down for various silly reasons, mostly involving holiday schedules and regular maintenance. Also, bear in mind that while today we know how to breed them, back then they didn't, and going to all that trouble for something they didn't even know if they could accomplish must have seemed unwise. Somebody would have had to PAY for all of that, after all.
Probably the worst thing they did, in my own lame opinion, was letting too many people have too much access to the collection site data, which in turn led to the rest of the REAL damage. Oh well, better that than letting the other hotspots become too well known, I guess. Maybe that site will even recover someday now that everyone thinks it's not worth visiting.
All in all, while it may be irksome, they did the best they could with what they had at the time, and we gained a lot from it. It's easy to look back with hindsight and complain, but give 'em a break. Besides, this sort of thing isn't likely to ever happen again with today's advances.