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Blending Fishery Science with Everyday Fishing

Lakeshore Development and Bass Growth

Anyone who has fished for long enough has noticed an increasing number of houses on the shores of some of their favorite water bodies. While this might result in more docks to cast lures to, development can have negative effects on fish, including less input of wood to the water body, lower densities of aquatic vegetation, and changes to aquatic food webs.

Researchers examined the effects of lakeshore residential development on growth rates of largemouth bass in 16 Wisconsin lakes.* Development ranged from 0 to 45.8 buildings per 0.6 miles of shoreline (within 328 feet from the shoreline). A significant relationship was found between lakeshore development and largemouth bass growth. Growth rates of bass less than 8.3 inches increased with increasing development. However, growth rates of bass greater than 8.3 inches decreased with increasing development. Overall, bass in highly developed lakes took 1.5 growing seasons longer to reach 14 inches.

Growth rate results for larger bass are similar to those of a previous study, but the finding of faster growth of smaller bass appears to be new information. Based on previous studies, the researchers suggest reasons for the size difference in growth response: Growth of small bass could increase due to decreased competition as development has been shown to reduce lake-wide abundance of small fish; decreases in aquatic vegetation linked to development can result in faster growth of small bass; an increase in angling pressure associated with development could change growth rates via harvest or catch and release. Regardless of the reason, anglers should keep in mind that largemouth bass in highly developed lakes may take longer to reach a size preferred by anglers compared to undeveloped water bodies.

lakeshore

Managing Sunfish Separately

Since the dawn of modern fishery management, bluegills, redear sunfish, longear sunfish, pumpkinseeds, and other sunfish species have typically been lumped into one category in state regulations. In the past, bag limits tended to be large, or even unlimited, and length limits rare. But new approaches to managing sunfish have shown that fishing can be improved by crafting regulations to the life history of the species and its population characteristics.

Biologists from Alabama and Georgia studied bluegill and redear populations in three reservoirs, determining growth and mortality (fishing and natural), and assessing size structure.* They then used a computer simulation to predict the effects of length and bag limits on each species. Presently, bag limits in both states are 50 fish per day with no length limits.

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The analysis revealed that the two species have divergent life history patterns that make redears far better candidates for minimum-length limits and bag limits than bluegills. Redears grew faster than bluegills, especially at greater ages, and lived considerably longer, up to 9 years of age in each of the reservoirs, with a good number of fish living 6 or more years. Bluegills, in contrast, had higher mortality and few lived more than 4 years. Most importantly, redears reached preferred size of 8 inches 2 to 4 years younger than bluegills.

Implementing a 7-inch limit on bluegills would reduce the number harvested by anglers as much as 70 percent and decrease yield 40 to 50 percent, while increasing the number of preferred-size fish two to four times. Yet for redear sunfish, an 8-inch limit would reduce total harvest less than 20 percent by weight, while boosting the number of preferred-size fish (8 inches) from 5 to 20 times, depending on body of water. The biologists note that while redears in southern reservoirs spawn only once in spring, bluegills may spawn monthly during spring and summer months, increasing their rate of fishing and natural mortality.

In contrast to bluegills, redear sunfish populations appeared to show substantial benefits to size structure when minimum-length limits were applied. At this point, there’s not enough life history and population information for other sunfish species in other regions to suggest that they be managed separately.

Record Flathead Resurfaces

maxresdefault-3On May 14, 1998, a 123-pound flathead catfish was caught by Ken Paulie from Elk City Reservoir, Kansas, that shattered the existing world record by over 30 pounds. However, nothing more than weight, length (61 inches), and girth (42.75 inches), were recorded from the fish at that time. As quickly as the fish appeared, it vanished from the public eye. Biological questions about the fish were never answered and it appeared they never would be.

Paulie kept the fish in a freezer in hopes that it would financially benefit him. This past winter he gave the freezer to his son-in-law with the condition that the sonin-law clean the freezer out. He found the fish and gave it to one of his buddies to make a European mount. In February, 2016, nearly 18 years after the catch, that person called me and asked if I wanted the carcass.

The biologist that initially verified the fish in 1998, Sean Lynott, joined me to see it and it was quickly clear that it was the fish. It still had the same rope stringer in its mouth and was wrapped in the same blanket that Lynott recognized from 1998. We collected pectoral fin spines, vertebrae, and dorsal fin spines to estimate the fish’s age.

We also conducted a partial necropsy to determine sex and stomach contents. With help from biologist Jeff Koch, we estimated the age of the fish at 22 years. The fish grew quickly through its first 5 years and then rapidly through its next 5 years. Growth from ages 11 to 22 was typical of a fish that age.

The necropsy revealed the fish was male. There also was a 28-inch bigmouth buffalo in its stomach. Decomposition of the buffalo didn’t allow us to determine it’s true weight, but typically a buffalo that size would weigh around 14 pounds. With that kind of diet, it’s no wonder this fish got so big so quickly.

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