In Southeastern Pennsylvania, spawning begins in early June or when the water temperature approaches 70 F. In the summer of 1992, while on a fishing trip in mid June, I was able to observe Bluegill, Pumpkinseed, and Redbreast Sunfish performing their spawning ritual. The spawning species were verified when I caught a few of the fish on my fishing rod. I was not able to observe the nest building process, as the males had already completed this task and were guarding their nests from all intruders. The nests were constructed in water less than 12 inches deep and closely spaced (the edge of the nests touching adjacent nests). In the spawning ritual, females approach the males and begin circling each other with fins fully extended. After a short time the pair stops circling and the female tilts her body to a 45 angle. The eggs are released and simultaneously fertilized by the male. The females rarely spawn with only one male. They generally move on to other males to complete spawning while the males remain on their nests to guard the eggs.
Throughout the summer of 1992 I collected several green sunfish for my aquarium. Some had to be returned to their original body of water due to conflicts with the other sunfish already in the tank. Eventually I was able to collect two individuals of the same size that got along with minimal fighting. A third juvenile green sunfish and brown bullhead catfish, about the same size of the others, found in a local pet shop were also added. Amazingly, all four fish got along. Being juveniles I had no way of accurately sexing the sunfish, but I hoped that I had captured a pair. In Pennsylvania, my understanding is that Sunfish can be legally collected with a fishing rod and valid fishing license. Instead of taking them home to fillet, they accidently found their way into my aquarium. As long as the fish are cleanly hooked in the mouth, they suffer no ill effects and are feeding by the first or second day. I maintained the fish all summer in a "community" style 20 gallon high aquarium in my outdoor shed. The shed is equipped with a thermostatically controlled exhaust fan to prevent heat buildups. The average summer temperature of the aquarium water was about 80 F with a pH of 7.0. No other attempts to alter water chemistry were made. Filtration was provided by a Fluval 3 internal power filter connected to a spray bar and a Penn-Plax clear-Free corner filter (Model CF-1). Drift wood, small rocks, a flower pot turned on its side and about an inch and a half of gravel were provided along with the aquatic plants Vallisneria, Ludwigia, Sagittaria, Bacopa and Elodea (Anacharis). Anacharis grows wild in the waters where I caught the sunfish. The plants do moderately well in the summer, but really thrive and grow quickly in the winter when the water temperature is below 50 F. The tank is enclosed in a plywood box with removable lid insulated with styrofoam. An air space of about 4 inches surrounds the sides and top of the tank. Minimal heating is provided using a voltage regulator connected to heat tape. The heat given off by he heat tape warms the air space. This warm air is pumped into the tank by the air pump and effectively prevents freezing or major drops in temperature. The heat is manually controlled and used only when excessively cold. In the summer the sunfish are fed moderately heavy every second or third day and in the winter they are fed sparingly every three or four days whenever the water temperature rises above 50 F. Below 50 F the food in their stomachs digests so slowing that it can actually spoil before digestion is complete, killing the fish. Besides, I am trying to recreate their natural environment, and minimal feedings in the winter is part of it. The foods offered include fresh frozen mummichogs, grass shrimp and Atlantic silversides, grasshoppers, crickets, nightcrawlers, chicken heart, freeze dried krill, freeze dried daphnia, freeze dried shrimp, dry cichlid pellets and any other insect I can catch. The Mummichogs, grass shrimp and Atlantic silversides were caught with a minnow trap and net while vacationing at the beach. These foods are their staple winter diet when the regular live foods are not available.
There are no provisions to chill the water in the summer. The fish endure an average summer temperature of 80 F and an average winter temperature of about 40 F. Forty percent water changes are generally made once a week in the spring and fall but usually every few days in the summer. Twenty-five percent water changes are made about once a month in the winter (when water temperatures are consistently below 55 F). Don't be lax with water changes. These fish have big appetites and produce large amounts of waste. It is extremely important that all water added to the aquarium during water changes be the same temperature as the water in the aquarium or temperature shock to the fish will result. This group of fish were overwintered as naturally as possible in the hope that they will be properly cold conditioned and ready to spawn in the spring. As soon as the weather began to warm another 20 gallon high spawning tank was set up in the shed. Except for the gravel and sponge filter the tank was kept bare. A chiller unit was utilized to maintain an optimum temperature (70 F) for spawning and raising fry during the hot summer months. In April, 1993 as the water temperature slowly increased two of the sunfish began to swell with eggs but the remaining sunfish did not exhibit any male behavior or female egg development. By the end of June, 1993 nothing had changed and I decided to release that fish to its native waters and attempt to capture another fish in the hope I could find a male. Fishing was poor the day I went out and was only able to catch one beautifully colored juvenile green sunfish. I was hoping its bright coloration meant it was a male because none of the other fish I captured showed such color. As the fish matured (he more than doubled his size in three months) I realized it was a male and hoped it could be induced to build a nest and spawn. October approached and by this time I was becoming frustrated because I had already put a year and a half of effort and alot of money into this experiment and did not want to wait till next spring to see if spawning would occur. November began and no interest to spawn was shown by the fish. The beginning of November was warmer than normal and the temperature in the community sunfish tank spiked about 8 F in a short time period. The male sunfish began excavating gravel in all areas of the community tank. When male sunfish are ready to spawn their colors intensify, they excavate a nest in the gravel and await a receptive female. Even though the male sunfish appeared to be excavating a nest and I noted his colors were brighter than normal I paid no attention to what he was up to.
On November 15, 1993 I checked on them at 10 PM and every thing seemed as it should. However, when I went out to check on them at 10 AM on November 16, the male was stationed in the middle of the nest and had all the other fish pinned in the opposite corner of the tank and would not let any of them out. I thought this odd behavior but I still had not realized what had occurred. I looked at the larger female who the night before was loaded with eggs and saw that she was as thin as a rail. When I quickly looked back at the male I noticed eggs, hundreds of eggs. They had spawned over night and the male was protecting the eggs. The fertilized eggs are adhesive, perfectly round, colorless and approximately 1/16 of an inch in diameter. I quickly removed all the fish except the male and put them in the spawning tank. The spawning female was a bit ragged with torn fins and the other fish were all in good shape. The fluval filter and spray bar were removed and replaced with an air driven sponge filter to ensure that none of the eggs or fry would be sucked into the filter. Air flow was high enough to cause a light current in the aquarium. The current prevents any harmful material from settling on the eggs and wigglers. A 25% water change was also made. The community tank was not intended for spawning and was in need of a change anyway. On November 17 I noticed that any eggs kicked up by the male were quickly eaten so I took him out and put him in with the other fish. I now anxiously waited for the eggs to hatch. No chemicals were added for egg protection. Clean, well filtered and aerated water is sufficient. Based on my reference books sunfish eggs hatch in 3-5 days at 80 F and quicker at cooler temperatures. On November 19 the eggs finally hatched. It only took 3 days at a water temperature of 65 F and a pH of 7.0. There were no apparent problems with bacterial or fungal infestations of the eggs as evidenced the large number of eggs that hatched. With a little care and the heat tape turned way up I was able to maintain the tank to within plus or minus 2 F of 65 F to ensure proper incubation of the eggs and development of the wigglers into fry. The wigglers were entirely clear, no visible markings could be seen. Within 24 hours (November 20) eye spots became apparent and the wigglers started to take the form of fish 24 hours after that (November 21). Fifteen to twenty-five percent water changes are made every day and so far all is well. With regard to how long it takes for the wigglers to become free swimming my references estimate about one week. On November 25 I noticed a few fry making their first attempts at swimming on their own. I offered a very small quantity of brine shrimp but none were accepted. No further offerings were made until the 27th. This was the eighth day since hatching and dozens were free swimming. I again offered a very small quantity of brine shrimp and for the first time the fry began feeding. By the ninth day all were free swimming and brine shrimp feedings began twice a day, once in the morning and once in the evening. The feedings require that the aeration and filtration be turned down to a minimum. This prevents the shrimp from being sucked into the filtration system and because the fry are somewhat uncoordinated they cannot successfully capture the moving shrimp in moving water. With still water it takes them several attempts before they can capture the shrimp. This will quickly pass as the fish grow and become proficient swimmers. It is easy to determine which fry are feeding. Since their bodies are still transparent, consumed shrimp give the fry orange bellies.
Two months have passed and the majority of the fry are now one inch or larger. The remaining fry number about one to two hundred. The fry that were unable to swim properly and/or feed consistently quickly died. At first several fry were dying daily, but now virtually none are dying on a regular basis. I figured I lost about 100 fry to what I will call natural selection. At any rate, their survival is by far better than it would be in their natural habitat. Due to limited space, I am experiencing cannibalism of the smaller fry by the larger fry because I am unable to provide the tanks necessary to separate out the larger fry as needed. The fry are still mostly dependent on brine shrimp, but will be weaned off the shrimp as soon as they are large enough and can be persuaded to accept other foods. Even after two months most of the fry still do not resemble their parents, i.e. their pelvic fins are not yet visible (dorsal and anal fins are faintly visible) and their bodies are still substantially transparent. I will consider them juveniles when their body shape and coloration resembles adult sunfish. This is expected to occur in the next one to two months. This experience has been very rewarding and helpful in understanding the life cycle of the Green Sunfish as well as Sunfish in general. I look forward to spring when I hope to experience another spawning of the Green Sunfish.