Pond Boss Forums INTRO Questions & Observations Genetic changes by culling largest fish!

Here is the news release but no access to the paper:

http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=1224

This is a amazing finding which suggest those that want to produce world record Bass should only let the largest bass spawn. This also suggests that overcrowding or producing fry from smaller fish, will also produce a genetically inferior variety of bass or any species.

Has Texas DPW's (sic?) Lunker LMB breeding program shown any verifiable results yet?

Having been raised on a livestock farm, it makes sense to me. Raising cattle, you pick out and keep your best heifers and bulls to breed. In fishing / hunting, people tend to harvest the fastest growing or biggest fish or deer. Hopefully, those fish or deer had already passed on their genetics, but... This study might address catchability too. Those aggressive hitting fish tend to be the ones on some one's dinner plate.

Good point Theo! That should be the way to select for the most agressive, largest, fastest growing if it works.

The difference that this study suggests is that only the largest fish will spawn and create larger fish. In the past we thought that if you crossed the largest fish, the young from that would have the "big fish" genes and if you crossed the young at a smaller size you would retain that trait. I am sure the "big fish" gene is still active but somehow diminished by the smaller fish spawning. Some of you with fish biology degrees help me out.

I think we've all heard the ideas about letting the big ones go so they can get bigger, or whatever they do. I'm guessing that the idea was based on a common sense logic without any real substantiation.

This study is very interesting. We'll have to get a copy of the whole study somehow so we can see if a lot of questions get cleared up regarding the study.

A couple of questions come to mind:

1) Do you think that by leaving the largest fish (in a control setting), the existing largest fish will control the overall population by cannibalism, thus reducing the overall population, thus leaving more food amongst fewer fish; eventually leading to the existing larger fish getting larger?

2) Do the largest fish tend to breed with other larger fish?

I'm guessing the full study will answer a lot of questions.

I've always contended anglers are their own worst enemy. Case in point:

I have an old text book that did a survey on a local natural lake at the turn of the 20th century. THEY WERE HARVESTING 14 INCH BLUEGILLS IN THE SURVEY! 14 INCHES! And these were not hybrids. That lake or none that I know of produces 14 inch bluegills anymore.

After posting this I began to wonder if I had not jumped to conclusions about this, not having read the paper. I emailed the autor and he very gratiously sent me a copy of the paper. The jury is still out on exactly the mechanism of the genetic change:

From the paper:
Many fitness correlates decreased as a result of harvesting the largest individuals in the population. These correlated responses could be indirect responses to a harvest-induced decline in maternal size or adaptive responses to the new fitness landscape. Regardless of the mechanism, they decrease the intrinsic capacity for the population to rebound under natural conditions. A new Darwinian fisheries paradigm is needed in order to account for such impediments to recovery and to ensure sustainable yields over evolutionary time scales.

Anyone who would like to read the paper send me a PM with your email and I will send it to you. Sunil I am sending you a copy.

Theo- Here is a list of the acomplishments of the share a lunker program. The only progress they list is keeping the fish alive. :rolleyes:

http://www.tpwd.state.tx.us/spdest/visitorcenters/tffc/budsharelunker/accomplishments/

Even the fish have benefited from the ShareLunker program. When the program began, little was known about the procedures needed to care for big bass. Early in the program, many entries died while at TPWD facilities. Over time better care has increased survival to the point that nearly all fish entered into the program survive to be used for spawning or are returned to the wild. Even more importantly, proper fish handling techniques have been publicized as part of the program, so that anglers are now able to take better care of any fish they catch.

Ponds :

Send me the paper at my email above and I will take a look and report back.

I have read hundreds of studies and can state that they each one has to be examined closely and often one can not infer very much or far with their conclusions. One difference I always note first is was it from field studies or in the lab. In some studies that alone can make a world of difference. It is next to impossible to compare results form one fish species and extrapolate its results to another species that it is not closely related to genetically. Unfortunately some studies are written with a purpose in mind to advance an idea for reasons other than science. For what its worth one very good fisheries text has a chapter on how to look at studies and how they were set up to see if they are valid or not. Most good fisheries organizations have very tough and stringent peer review before they can be posted. I have even found papers that were well planned and subject to the strictest peer review from excellent fisheries scientists that found opposite results which can not be explained.

Has someone emailed me a copy of this paper?

I got an email from someone and it just says "I have attached a copy of the paper."

Just want to make sure before I download it.

Thanks.

Share a lunker update -- TPWD is now in a phase of tracking the results of tagged offspring (from the program's lunkers) with known genetics in selected lakes so that they can id the offspring of those offspring when caught years later to see if genetics for large size are heritable when compared in a natural envior.

Sunil- From message above:

"Anyone who would like to read the paper send me a PM with your email and I will send it to you.

Sunil I am sending you a copy."

Thanks PF2. I had missed that.