Age and Size of Yellow Perch from Lake Ontario and Cayuga Lake

In the fall of 2025, Dr. Karboski partnered with local fish processor Tom Allen of A-Tom-Mik Manufacturing in Oswego, NY to supply commercially processed yellow perch for her students to study.

Freshly caught yellow perch from Lake Ontario, supplied by Tom Allen of A-Tom-Mik Manufacturing, Oswego NY.

Tom caught the perch by hook-and-line angling from both Cayuga Lake and Jefferson County waters of Lake Ontario. Tom typically fillets the fish he catches, then sells the meat to local restaurants and buyers. Dr. Karboski’s students took the filleted carcasses, along with some perch heads with the bodies removed. Dr. Karboski also purchased some whole, un-filleted perch so that her students could collect weight and diet data. 

Lake	Sample Condition	Number
Lake Ontario	Whole Fish	62
Lake Ontario	Filleted Carcasses	16
Cayuga Lake	Heads Only	49
	Total	127

Methods

Back at the lab, the students measured and weighed the whole fish, then extracted otoliths (ear bones) and the stomachs for later diet analysis. For filleted carcasses, the students measured the total length of the fish and extracted the otoliths. For samples with only a head, the students extracted the otoliths and then measured the opercular length, which is the distance from the tip of the perch’s nose to the end of the bony plate covering the gills. Students were able to estimate the total length of the fish from opercular length using an equation from Timm (2024). These estimated lengths were used in the following analyses. 

Head measurements of yellow perch from Timm (2024). Opercular length is the distance from the tip of the nose to the end of the opercular flap.

Otoliths are the ear bones of fish, and they grow in rings like trees. These rings can be counted in order to estimate the age of the fish. Otoliths were mounted in a block of epoxy, then a thin slice was cut from the center of the otolith block using a Buehler IsoMet saw. These thin slices were then glued to microscope slides, and the rings were counted under the microscope.

A sectioned otolith from a 5-year-old yellow perch. Age is determined by counting the number of dark bands. Photo by Machara Malone, BIO 492 Fall 2025.

Results

Commercially processed yellow perch were between 1 and 6 years of age. Unsurprisingly, older perch were larger, with perch growing about 19.6 mm (0.77 in) per year on average. However, there was a lot of overlap in length between ages, which means that just looking at a perch’s length won’t necessarily tell you how old it is. The largest perch caught was a 5-year old, 345 mm (13.6 in) long fish from Lake Ontario. The smallest perch caught was a 3-year old,  204 mm (8 in) long fish, also from Lake Ontario. There were no differences in the lengths or ages of fish from Cayuga Lake and Lake Ontario - fish from both lakes were of similar ages and sizes. 

Length-at-age for commercially processed yellow perch from Lake Ontario (purple) and Cayuga Lake (green). Total lengths (nose to tip of tail) are presented here in both millimeters (mm) and inches (in). Total lengths for perch from Cayuga Lake were estimated from opercular length using the equation in Timm (2024). There was no significant difference in length-at-age between the two lakes.

Students only weighed whole fish, which means that the following graphs are showing data from Lake Ontario fish only (all Cayuga fish were just heads!) Also unsurprisingly, perch got heavier as they grew older (gee whiz!), with fish gaining 28.3 g (about 1 oz or 0.06 lb) per year on average. But just like with length, weight was quite variable over the different ages. There were many younger fish that were just as heavy as older fish. This is likely due to differences in foraging success, health, genetics, and other factors that affect the growth rate of fish. Notably, our heaviest fish was not our oldest fish. The heaviest fish was a 447 g (0.98 lb) whopper who was just 4 years old. That’s at the upper end of the scale for a yellow perch!

Weight-at-age for commercially processed yellow perch from Lake Ontario. Weights are presented here in both grams (g) and pounds (lb).

While we didn’t see a strong relationship between weight and age, there was a very close correlation between weight and length. Again, unsurprisingly, as fish grew longer they got heavier. Fulton’s condition factor (K) is a measure that tells us how heavy a fish is relative to its weight - fish with a higher condition factor are chunky and have more energy reserves, whereas fish with a low condition factor are skinny and may be having trouble finding food, suffering from disease, or dealing with other stressors that affect their growth. On average, the Fulton’s K condition factor was 1.44 ± 0.13 for Lake Ontario perch. This number doesn’t tell us much on its own, but we will be able to compare it to the condition factor of fish from future years to see how the condition of perch changes over time. For example, if we see the condition factor start to drop, that may indicate that perch are having a harder time finding food or are experiencing stressful conditions. 

Length-weight regression for commercially processed yellow perch from Lake Ontario. Length is presented here in both millimeters and inches (mm/in), and weight is presented in both grams and pounds (g/lbs).

These results give us a good baseline knowledge of yellow perch age, length, weight, and condition in Lake Ontario and Cayuga Lake. By tracking these numbers over several years, we can keep an eye on the health of the perch population in order to ensure a sustainable yellow perch fishery in the future. 

Examining a sectioned yellow perch otolith under a compound microscope. Photo by Dana Fortney, BIO 492 Fall 2025.

Special thanks to Fall 2025 senior capstone research students Dana Fortney and Machara Malone for processing and aging the majority of the yellow perch used in this study. Additional thanks to students in Dr. Karboski's ZOO 441 Fisheries Science and Management class, who processed and aged additional perch in Spring 2026.

References

Timm, A. 2024. Specific measurements of a yellow perch head compared to the total length. Journal of Earth and Life Science 66. https://pines.bemidjistate.edu/j-earth-life-sci/66/