Can the decreasing size of fish due to fishing be reversed? Perhaps

 
The common practice of catching only the larger fish in a population becomes an evolutionary pressure for later generations to stay small and grow slow, a problem seen emerging with a number of fish species commonly taken for food. A recent study suggests that it may be possible to reverse this effect.
 
To address the question, researchers caught hundreds of silversides (Menidia menidia) in Great South Bay, N.Y. The researchers divided them into six populations. For two groups, researchers routinely caught the large individuals, taking all but the smallest 10%. They targeted small fish in two of the other groups, and removed fish randomly from the remaining two groups. After five years (approximately five generations), the population of the two groups from which the larger individuals were removed had a smaller average size than the comparison groups.
 
Then for the next five years, researchers kept the populations as established at the end of the first five years, but thereafter changed the rules. Instead of "fishing" based on size, they removed fish randomly from all six groups. At the end of the five years, the shrinking trend had reversed, and adults in the two populations from which large fish had formerly been removed had, on average, regained half their original length.
 
The researchers noted that although size increase incurred, it was slow; also size increase did not occur as fast as it shrank. If the silversides maintained their current pace, the researchers calculated, they will need 12 years (12 generations) to return to their former size.
 
However, whether this experimental result would apply to fish in the wild is uncertain. Further, assuming it might apply, one needs to take into account that seven years is not unusual for the life span of a commercial fish species. Thus, twelve generations, even assuming other species matched the silversides' speed for recovery, could take 84 years to recover size. Thus, the researchers argue that the best path is to avoid the evolutionary shrinkage to begin with or to stop it as soon as possible.