Case Studies in Fisheries Conservation and Management: Applied Critical Thinking and Problem Solving
Case 21: Northern Pike Reproduction and Early Life History: Ties to Recruitment Patterns
Depending on the fish species, and sometimes even the population, recruitment typically is related to habitat, environmental factors, or both. In this case, you will assess the reproduction and early life history of the northern pike. Then, we will ask you to use your new-found knowledge to devise a future management strategy.
Recruitment seems to be a straightforward term, but you will find that its definition can be rather slippery. Probably the most accepted definition of recruitment within the fisheries profession is the number of individuals hatched in any year that survive to reproductive maturity. However, alternative definitions might include the number of individuals that reach harvestable size, a particular size or age, or the minimum size captured by a particular sampling gear. In the title of this case study, you could replace “recruitment” with “year-class strength.”
Prior to undertaking this case study, it is essential that you understand north¬ern pike 1) spawning behavior, 2) spawning habitat, 3) behavior of newly hatched fry, and 4) nursery habitat. Information can be found in fish iden¬tification books, such as Scott and Crossman (1973) or Eddy and Underhill (1974). Books on fishes from states or regions with northern pike would like¬ly contain similar information. Much of this information might also be found on internet web sites, such as http://www.fishbase.org/search.cfm or http://hatch.cehd.umn.edu/research/fish/fishes/natural_history.html (both sites ac¬tive September 2009). Finally, your college or university library may provide online literature or database searches with engines such as Fish and Fisheries Worldwide or Google Scholar. Searches on such sites with specific key words can be highly useful to locate scientific articles with the specific information that you seek. Learning how to access such information can be challenging but is an important skill to master.