Banded pygmy sunfish Elassoma zonatum are a species of Pygmy sunfish

Pygmy sunfish

Elassoma is a genus of freshwater fish, the only member of family Elassomatidae and suborder Elassomatoidei of order Perciformes. The type species is E. zonatum, the banded pygmy sunfish. The Elassomatidae are known collectively as pygmy sunfishes, but are not true sunfishes, which are members...

Abstract

The following is a monitoring plan for the Banded Pygmy Sunfish (Elassoma zonatum). The plan will cover this pygmy sunfish’s geographic distribution, ecology, life history, current management, and recommended future management plans. The distribution of the members of Elassomatidae are varied. While many are confined to smaller areas, the banded pygmy sunfish has the advantage of a wide range of habitat. This particular species has been fortunate in not losing much habitat over its history. Being an Eastern United States species that lives in slow water condition, they take to living in coastal plain habitat primarily. This leads directly into their ecology as being a wetland species gives them a strategic advantage over other fish species. This allows them to outlive other fish in hypoxic water conditions. In fact, such habitat allows them to breed and forage for food in relative safety. Being a resident in such habitats, it is easy to imagine a few things of their life history. Banded pygmy sunfish are small fish that use as little activity as possible. This is a strategy that allows for energy and oxygen conservation in such eutrophic habitat. Despite the usual low amount of activity, they are active breeders that spawn multiple times a year in cool to warm water conditions. They mature quickly to make up for a shorter life span. No management currently exists for the species as it is in good standing on federal and state levels. The only true problem that is obvious is the disappearance of wetland habitat on a continental level. This could prove to be a huge future problem for this species as it has for other members of Elassomatidae. Therefore, the recommended management section of this paper includes some details on keeping the species in good standing in the future.

Geographical Distribution

The banded pygmy sunfish (Elassoma zonatum) is a dwarf fish that spans widely in several different habitats. They can live in rivers, streams, lakes, ponds, and even swamps. This species is historically found only in the continental United States with relatively little change in distribution. One exception to this is minor decreases in species distribution due to habitat loss. They have historically been residents of the Mississippi river drainage system and gulf coastal plain region. Currently they span from the lower Roanoke River drainage in North Carolina to the southern to middle parts of St. Johns River in Florida. Also they are found west to the Brazos River drainage in Texas and north to lower Wabash River drainage in Indiana and Illinois. Being a member of Elassomatidae, this species of pygmy sunfishes is no different in habitat strategy. It prefers to live in slower to still water conditions with higher sedimentation content, hence the swamps and ponds. However, the human development of wetland habitat over the ages has caused a decrease in banded pygmy sunfish and other pygmy sunfish habitat. Even though the banded pygmy sunfish can retreat to lakes, streams and rivers when wetlands are being drained, they need the wetlands for breeding. Thus the true reason for the disappearance of the banded pygmy sunfish from certain areas is not just a loss of any habitat, but the loss of its breeding habitat. When this happens, the population eventually dies off leaving an area that can no longer support the species.

Ecology

Stomach contents of 46 individual banded pygmy sunfish (26 of which were spawning adults) collected at Mound, Louisiana were examined for food identification by Barney and Anson. The main food identified at Mound included insect larvae (mostly from the family Chironomidae), small crustaceans and snail eggs. The crustaceans and snail eggs combined constituted the majority of the content. Next in quantity was the insect larva. It is also noted that minute amounts of algal spores were ingested by these fish. It is most likely that these algal blooms were taken in accidentally with other prey. Lastly, no other fish species or banded pygmy sunfish larva were found in the stomach contents. The banded pygmy sunfish is a species that lives in rather eutrophic conditions such as swamps and ponds. They are able to live in sedimentation levels that make oxygen availability less than 0.5 mg/L of water. This condition is termed hypoxia in which very few fish species can survive. The only other notable fish that have an impact on Elassoma zonatum are live bearers (Poeciliidae), the grass pickerel (Esox americanus) and bowfins (Amia calva). The bowfins are known to be occasional predators on the pygmy sunfish family. Occasionally the grass pickerel and live bearers are competitors for food with the pygmy sunfish. Other than fish, water snakes and fish eating birds are known to be enemies. Water beetles and Ondonta nymphs are known to be competitors for insect larva. It was noted that wetland habitat is important for spawning habitat, but it is also an important habitat for food and protection. It provides dense plant matter (especially Ceratophyllum) for cover against predators and as a laying area of snail eggs. This kind of habitat is also excellent as a source for insect eggs and larva. Thus, the human development of wetland habitat not only affects just Elassomatidae, but several other species of fish and insect as well.

Life History

Banded pygmy sunfish are spring spawners which usually spawn mid-march. Eggs are laid on ceratophyllum if it is available as it is in most wetland areas. If there isn't any ceratophyllum or similar vegetation available then eggs are scattered out on rocky bottoms in still water. The entire spawning process takes approximately 5-6 minutes. After the eggs are laid the male will chase the female away from the nest site since she would cannibalize upon the eggs. This species of pygmy sunfish can spawn 2-3 times in a year as determined by ova regrowth. Anywhere from 96-970 eggs will be in a clutch depending on a female size range of 2.25 cm to 3.5 cm in length respectively as well as on the fecundity of the female. Egg diameter will range from 3.7-3.8 mm on average. The egg, on average, takes 110 hours before it begins to hatch. The newly hatched larva are tadpole like in shape with four pairs of gill arches with a rhythmic gill movement. The eyes are without pigment and no mouth is developed upon this stage. Protein from the yolk enters the body through diffusion into a blood stream until the mouth is fully developed. Larvae are recorded anywhere from 3.5-3.7 mm in length and the juveniles are anywhere from 8.0-8.5 mm in length. The time it takes for newly hatched larvae to mature into full grown adults is on average 100 days. Cooler temperatures of 21-23 degrees Celsius is optimal for growth. It is also important to note that adults sexually mature at one year of age. The average lifespan of a banded pygmy sunfish is around 2.5 years of age with the maximum recorded age at 3 years.

Current Management

Certain members of Elassomatidae have been listed as threatened species but the banded pygmy sunfish is one of the few that is widespread enough to stay off that federal list. No state agency has listed the banded pygmy sunfish as threatened either. Habitat loss is the most immediate threat to this species. As wetland habitat is lost due to industrialization and agriculture breeding habitat and important food species disappear with it for Elassoma zonatum. Efforts are in place today to manage wetland habitat across the country. The federal standards of the USDA are to retain a minimum of 2% wetland in every state territory in the Eastern United States. While no agency or refuge is set up to protect this species, the conservation of wetland habitat acts as an umbrella for the species to keep up its population numbers. Fortunately, they are a resilient species that can survive in eutrophic conditions and warmer temperatures. Albeit, optimal spawning temperatures for water are 21-23 degrees Celsius. It is also noted that while some members of Elassomatidae can hybridize, Elassoma zonatum can not.

Recommended Management

The abundance of this species across its native range has not been calculated, but point count observations have kept it off of the threatened species list. Monitoring of this species has been done by seining populations and performing sample counts. This method seems to work well for this species and should be continued to estimate their abundance. Sampling should be done by setting the boundaries of the species range and randomly selecting quality sites they could be found in (such as swamps or ponds along the gulf coastal plain) and sampling in that location. The sampling should be done every 2-3 weeks in areas where a population exists in the spring and fall. As mentioned before, wetland habitat destruction is the foremost issue concerning the banded pygmy sunfish. Providing protection and reconstruction of wetland habitat along the gulf coastal plain and Mississippi River drainage system would allow for more breeding habitat. It is also recommended that certain habitats with high population densities should be set aside for protection. So far, no invasive species have been noted that are a competitor or enemy of the banded pygmy sunfish.