Fishing in a Changing World: How Does Climate Change Affect Fishing? By Noah Bressman
During my freshman year in college in upstate New York (2013), the spring rainbow trout spawning run into the tributaries was fairly typical; it started in mid/late March, and ended in mid/late April. Since opening season for trout in the tributaries was April 1st, that worked out well for the trout since some of them had time to spawn uninterrupted. That also worked well for the fishermen since they had a chance to catch a lot of big trout during the run. However, during my senior year (2016), there was a particularly warm winter and the trout began their run around mid/late February. In terms of fishing pressure, that was great for the trout since they were practically done spawning by April 1st. However, fishermen missed most of the spawning run.
The extremely warm winter in 2016 compared to 2013 was partly due to the El Nino Southern Oscillation (ENSO), a global climate cycle that occurs about every 7 years. ENSO causes warmer than average temperatures in some years (like 2016), followed by cooler than average temperatures, along with shifting precipitation and wind patterns. Additionally, climate change can intensify ENSO conditions, shift weather patterns, make extreme weather events more common. A combination of El Nino conditions and climate change likely accounted for 2016 being the hottest year on record, according to the National Oceanic and Atmospheric Administration (NOAA). A common misconception about climate change is that it is synonymous with global warming. While the average temperatures of the Earth have increased since the start of the Industrial Revolution, climate change also refers to other changing climate conditions, like wind patterns and ocean currents. In turn, these conditions can cause extreme blizzards, cold snaps, hurricanes, and droughts. For instance, in the Piedmont of North Carolina (where I currently do most of my fishing), we essentially skipped spring; we had a long winter with low temperatures in the 30s and 40s all the way into the beginning of May, and an early summer with highs in the 90s in mid-May. Since bass typically spawn when the water temperature is 60-70 degrees, the pre-spawn bass fishing lasted a relatively short time. This was a bummer to many bass fishermen in the area (including me) because the pre-spawn bite can be the best time of year for bass fishing since the bass feed like crazy to fatten up for spawning. These unusual weather conditions were likely caused by a changing climate, which caused a shift in fishing conditions.
Rising temperatures may actually benefit some fishermen, though, because fish are ectotherms (cold-blooded). Their metabolism increases with temperature. Therefore, if the water temperature increases, the feeding and growth rates of bass and many other fish will also increase (Niimi and Beamish, 1974). Increased global temperatures may produce bass in New York that are bigger, grow faster, and eat more aggressively. However, there is a temperature limit at which the health of fish will decline. In the southernmost, warmest extent of their range, if water temperatures increase, native bass may not be able to survive as well, and those fisheries may suffer. Freshwater fisheries are likely to be hit the hardest by increasing temperatures because there is only so far north fish can migrate in a lake. In the ocean, however, some fish are able to migrate north or to deeper, colder waters to mitigate the effects of increasing temperatures. In fact, there is already some evidence of this. At the Mid-Atlantic Fisheries Management Council’s (MAFMC) meeting this February in Raleigh, NC, some scientists spoke to the council about how climate change is affecting saltwater fisheries. According to Bradford Dubik, a PhD Candidate at Duke University, over the past several years, commercial fishermen on the east coast have had to move northward by about 1 degree of latitude to catch the same species in similar quantities. The fish are moving north to cooler waters, and so the fishermen are having to move north after them.
As the climate continues to change, we may start to see changes in the types of fish we target in different regions. Historically colder trout waters may shift to bass-dominated fisheries, since bass can tolerate higher temperatures than trout. In ranges where bass are at their temperature limits, some invasive species, like peacock bass (which are native to tropical South America), may become the dominant species as they have evolved to survive in warmer conditions. We will likely have to change our fishing strategies to keep up with changing fisheries.
Niimi, A. J., & Beamish, F. W. H. (1974). Bioenergetics and growth of largemouth bass (Micropterus salmoides) in relation to body weight and temperature. Canadian Journal of Zoology, 52(4), 447-456.
Noah Bressman is a PhD candidate studying fish biology, functional morphology, and biomechanics at Wake Forest University. Below is Noah with a Rainbow Trout (Onchorhynchus mykiss), caught on a silver and blue Acme Kastmaster spoon with a single red hook, under a waterfall in a tributary of Cayuga Lake, NY.