Sunday, June 8, 2008

Lake Kabetogama and Voyaguers National Park

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Results from the 2006 large-lake sampling provided valuable information about the status of the fishery on Lake Kabetogama. The walleye population in Lake Kabetogama is suffering from low recruitment. Despite poor recruitment, the walleye gill net CPUE increased in 2006, after three years of steady decline. The increase observed in 2006 was interesting because young of the year walleye made up about 30 percent of the catch. Generally a large catch of YOY walleye in the gill nets does not mean much. However, in 2006 young of year walleye were captured in 17 of 20 gill nets; indicating a good distribution and representation in the fishery.

Aging of walleye otoliths showed that the catch is dominated by a couple of moderate to strong, year-classes; typical of a "boom and bust" fishery. For the fishery to recover a few strong year-classes need to be strung together, with some moderate year-classes filling the gaps. Currently walleye recruitment is inconsistent, with only a couple of strong year-classes still present in the catch.

Recently the 2001 year-class provided Lake Kabetogama with a bright spot in the net surveys. Early indications of the 2001 year-class were good. However, after observing several years of low relative catch rates, the 2006 catch rate was above average for age-5 walleye. The mean length of the age-5 walleye was 18.1 inches during the 2006 fall gill netting. Most of the 2001 walleye year-class will be protected by the new regulation during 2007.

The 1996 walleye year-class was also present in the 2006 gill-net catch. The 1996 year-class ranks as the strongest walleye year-class on Lake Kabetogama. This year-class has recruited to the protected slot (17 to 28 inches). Prior to the regulation change in March 2007, these fish would have been again vulnerable to harvest as they recruit from the protected slot to harvest length. The expansion of the protected slot will protect these fish for many years to come.

Results of YOY walleye surveys were good during 2006. Early season walleye growth was exceptional. The late July length projections indicate the best growth rates ever observed on Lake Kabetogama. This year's electrofishing efforts produced a moderate catch, indicating the 2006 walleye year-class will be average in strength. However, if growth indications prove to override abundance indices, the 2006 year-class could be the strongest year-class of walleye ever produced on Lake Kabetogama.

The 2005 year-class, despite indications of being an average year-class, was caught in below average numbers for age-1 walleye. Conditions for growth have been good for both the 2005 and 2006 growing seasons. Therefore, it would have been fair to assume more age-1 walleye would have been captured during fall gill netting in 2006. Their paucity in the 2006 survey may point to the issue of elevated juvenile mortality.

Gill net catches of the 2002, 2003, and 2004 year-classes have been below average. Similarly, prior to the 2001 year-class there were four consecutive years of poor to mediocre recruitment. The 2000, 1999, 1998, and 1997 year-classes were all below average in strength and help explain the current status of the Kabetogama walleye fishery. Fish from these year-classes ranged in length from 16 to 21 inches.

Sauger abundance bounced back slightly after three consecutive years of decline in abundance. The 2003 year-class provided a highlight in the 2006 net surveys. The 2003 year-class is showing great promise and should be recruiting to the sport fishery during the next couple of years. This year class will be the first strong sauger year-class since the two very strong year-classes of 1997 and 1998.

The 2006 fall gill netting indicates the northern pike abundance is holding around the 1.5 to 2.0 fish per net. Northern pike numbers have fluctuated between 1.5 and 2.5 per net for the last ten surveys. The pike population on Kabetogama has shown fluctuation in abundance; and may be nearing the bottom of the valley. However, while abundance may be down, the age and size structure are healthy. ?

1 comment:

Susie Lehto said...

I would be interested in updates to this information. I'm from Kabetogama, so I like to keep an eye on reports like this. Tipi on