|These guys like water!|
As some of you may know, I became a board member of the Big Hole Watershed Committee last spring. A big part of my involvement with the committee includes a monthly meeting in Divide. If you haven't heard of the Big Hole Watershed Committee it is a combination of all of the big hole river user groups (including a lot of ranchers) who work together to help protect and conserve the great resource that is the Big Hole River. The work that they do is incredibly important for the watershed, and in case you didn't know this or not, fish really like water, and smart management!
At our September meeting we had a guest speaker, Jim Olson from from MT FWP. Jim gave a great presentation and told us a lot of good stuff about the Big Hole. Here are a few of the interesting facts from Jim, check it out:
1. Big Hole River Fish Populations
Jim has been looking through historical fish data for the Big Hole. 1981 was the first year the Big Hole had a slot limit and that limit was expanded in 1988. The change can be seen in the fish data.
- Big Hole River near Jerry Creek: Slot limit had no effect on rainbow mass. Rainbow numbers low in high water years because they are spring spawners and high water increases mortality in the redds. Brown trout responded well to the slot limit. Prior the slot limit there were few browns. Today the brown:rainbow ratio is roughly 50:50.
- Big Hole River near Melrose: Both the number and pounds of fish per mile increased with the slot limit initially, then numbers flattened as the section reached carrying capacity. Before the slot limit there were many fish greater than 25 inches. Now there are few fish greater than 25 inches as fish have become smaller and not as fat.
- Big Hole River near Hogback (Glen to Notchbottom): This section shows the most impact from drought. The population in this section is down 1/3 from the previous section; however, fish in this section tend to be larger, likely due to less competition. Rainbows numbers have doubled in the last few years while brown populations remains flat. Jefferson River rainbows may be migrating into the Big Hole to spawn and causing the increase in number.
- Big Hole River near Pennington Bridge: 700 fish per mile and 1/2 of the population in the Melrose section. Limiting factors are water quantity, water temperature, and lack of habitat. There are no tributaries below the notch, except Birch Creek (which does not reach the river). The river in this section is stabilized with riprap, preventing the river from moving to create new habitat. As a result,BHWC recently completed a Lower Corridor Report to review alternatives for fish habitat in this section. BWHC has also proposed this section as a Drought Management Plan section, for review in 2013.
Question: In Melrose, why are there fewer rainbows than browns? Ans: Whirling disease. Melrose has a high rate of Whirling disease in rainbows, while above and below this section there is little effect. This may be due to local geology creating conditions that are ideal for worm survival. Young fish less than 4 inches and prior to their bones becoming solidified are most affected.