Late spring provides a wonderful opportunity for the gentle art of fish-watching

Peterborough Examiner  – June 7, 2024 – by Drew Monkman  

The delights of watching birds, mammals and a wide variety of insects are well known to nature enthusiasts. But only rarely do we turn our attention to fish. With the spawning season for many species now upon us, June provides an opportunity to see a host of interesting species and behaviours. Watching pumpkinseeds, bluegills and bass, or even non-game species like minnows and dace, can be almost as much fun as catching them.

Pumpkinseeds and both smallmouth and rock bass are all native to the Kawarthas, while largemouth bass, bluegills and black crappies have either been introduced or have arrived here on their own. All are members of the sunfish family (Centrarchidae). Bluegills are similar in appearance to pumpkinseeds but lack the face stripes. They also have a large, black “ear” spot on the back edge of the gill cover. It is not uncommon for these two closely-related fish to actually mate and produce hybrids.  

From top left clockwise: Pumpkinseed, Bluegill, Smallmouth Bass and Largemouth Bass. Photos by Scott Gibson

Nesting sunfish

Glimmering in the shallows on a sunny day, the pumpkinseed is the jewel of the sunfish family. Although its name comes from its flat, pointed, oval shape, the pumpkinseed’s colours are nothing short of spectacular. The red-orange belly and wavy blue and orange-brown stripes give this species an elegance few fish can match. But what’s interesting about the pumpkinseed doesn’t stop with its beauty. Its mating behaviour, along with that of the bluegill, is one of the most fascinating in the fish world.

In June through early July, male pumpkinseeds and bluegills construct a nest in the shallow water of lakes and ponds in the hope of attracting a female. The male sweeps away gravel and plant debris with his powerful caudal fin. At the same time, he holds his side fins out and pushes water forward so as to remain stationary. The nests are circular, about three times the length of the fish in diameter and often occur in colonies ranging from just a few to as many as 15. Males are very aggressive at spawning time and will charge any intruders.

The females remain in deeper water until the nests are completed. The male will then swim out and greet an approaching female and try to drive her into his nest. If he is successful there is an elaborate courtship process in which the two fish swim in a circular path with their bellies touching. As the female expels the eggs from her body, the male fertilizes them with his sperm. Not only will females often spawn in more than one nest but more than one female may also use the same nest. In fact, some nests can end up with more than 15,000 eggs. The tiny eggs stick to gravel or sand. If the water is warm enough, the young may hatch in as few as three days.

After egg-laying, the females depart for a summer free of domestic responsibilities. But for the males, their work is far from over. They must guard the eggs against predators and fan them with their tails in order to improve oxygen supply. Even after the eggs hatch, the males stay at the nest and guard the minute fry for about two weeks. These doting fathers will even retrieve babies that leave the relative safety of the nest by bringing them back in their mouths.   

Sneakers and satellites

Despite appearances, the business of spawning for male pumpkinseed and bluegill sunfish is far from straightforward. After expending huge amounts of energy building nests, defending territories and caring for the young, these hardworking dads can’t even be sure that they’re passing on their own genes. The hitch is that not all males are territorial and defend a nesting site. A majority of males actually rely on different mating strategies. One group, known as “sneaker males”, are much smaller in size and will actually slip into a territorial male’s nest when the female is releasing her eggs. The cuckolder will then release his sperm while the larger territorial male does the same. Although he may get chased away, another sneaker male will often dash in during the honest male’s absence.

To further complicate matters, another group called “satellite males” actually mimic females. Similar in age and appearance to the sneaker male, the satellite male tends to hover over the nest, acting like a non-threatening female. If a breeding pair of sunfish is present, he will then slowly swim down and release sperm during the spawning event. As a result of all this deceit, a majority of the eggs being cared for by the nest-building male have often been fertilized by one or more other fish.

Whether or not a male sunfish becomes a territorial, sneaker or satellite dad is completely under genetic control. A given male never changes from one strategy to the other during his lifetime. Territorial males don’t begin to build nests until they are six or seven years old and big enough to defend a territory. Sneakers, on the other hand, are sexually active by the age of two. However, they never grow as big as their honest brethren and usually die by five years of age, probably worn out from their promiscuous lifestyle!

In a given sunfish population, about four-fifths of the males are sneakers or satellites. But they never take over completely. When the number of territorial males becomes too low, there are not enough care-giving fathers for the sneakers to trick into raising their young. When this happens, some sneakers and satellites fail to leave descendants. This allows the number of territorial sunfish to increase until the balance is re-established.  

Bass: caring fathers

Anyone who spends time on our lakes and rivers in June is no doubt also familiar with the sight of a bass spawning in shallow water, often near a dock. Their aggressive nature at this time of the year is well-known, especially to bathers who may have experienced an unexpected thump on the leg.

Smallmouth and largemouth bass display similar spawning behaviour and even look very much alike. Largemouths, however, have dark, horizontal lines while smallmouths have vertical stripes. The largemouth’s upper jaw also extends past the eye, unlike the smallmouth’s jaw which is usually in line with it.

Smallmouth bass choose rocky, gravelly sites to spawn whereas the largemouth prefers a mud bottom. The male constructs the nest at a depth of about one metre, using his caudal fin to sweep a shallow depression free of loose silt and debris. The male and female then engage in pre-spawning rituals that involve rubbing and nipping each other. Eventually, the two rest on the bottom of the nest where the female deposits her eggs and the male releases his sperm. The female is subsequently driven off by the aggressive male. As many as three different females may deposit eggs in the same nest.

The male remains at the nest site to jealously guard the eggs and later to protect the young fry. After they hatch, the young bass swim in a school close to the nest with the male close by. He continues to perform bodyguard duties for about two weeks.

A few pointers  

Unless you decide to do your fish viewing from underwater with a mask and snorkel – a strategy that allows you to get surprisingly close – surface opacity is almost always a problem.  It can be reduced, however, by wearing polarized sunglasses which will lower surface glare. Viewing can also be improved if you’re able to look down from two or three metres above the water such as from a bridge. Clear, sunny days are best, especially when the sun is high in the sky. 

Next week, I’ll turn my attention to the behaviours of some of our extraordinary non-game species like fallfish, creek chub, dace and darters.

Atmospheric CO2

            The atmospheric carbon dioxide reading for the week ending June was 426.88 parts per million (ppm), compared to 424.62 ppm just one year ago. Today’s rate of atmospheric carbon dioxide increase is 10 times faster than at any other point in the past 50,000 years.

Drew Monkman

I am a retired teacher, naturalist and writer with a love for all aspects of the natural world, especially as they relate to seasonal change.