Labidesthes sicculus is commonly known as the brook silverside. Labidesthes sicculus belongs to the Actinopterygii class and to the Atherinopsidae family. L. sicculus lives in slow moving rivers and lakes from the Great Lakes to the Mississipi basin and Gulf Coastal plains. L. sicculus survives best in clear water with aquatic vegetation. L. sicculus feeds on a diet of copepods, insect larvae, and winged insects. The spawning season of L. sicculus occurs during the spring and early summer. The survival of freshwater fishes such as Labidesthes sicculus is increasingly threatened. In order to ensure survival of L. sicculus, turbidity of natural habitats should be monitored.

Geographic Distribution

The distribution of L. sicculus populations range from the Great Lakes southward through the Mississippi Basin and Gulf Coastal Plains (including 27 states and parts of Canada). It is native to the majority of this distribution, but has also been stocked outside of it’s natural range as forage food for sport fishes. . L. sicculus occupies freshwater lakes, ponds, quiet pools and small rivers. The environment ranges from cool to warm water with variability in levels of gradient and vegetation. Consistently, however, L. sicculus prefers clear water with low substrate concentrations. . L. sicculus is vulnerable to turbid waters. . In Tennessee, L. sicculus populations were shown to have decreased shortly after the construction of the Tennessee-Tombagbee Waterway. Populations likely declined because of introduced competition. .

Ecology

Labidesthes sicculus are on the lower end of the food chain, and are preyed on by many larger fish. The diet of L. sicculus consists mostly of zooplankton. They are highly specialized feeders with cladocerans comprising 80% of their diet, (40%) small flying insects, and (20%) midge larvae. Their diet varies with life stages and seasons. At a younger age L. sicculus prey mostly on smaller fish. Their diet shifts to immature insects later. During winter, L. sicculus eat mostly planktonic crustaceans . Because of both intentional and unintentional species introduction, L. sicculus must compete for food sources. Specifically, L. sicculus has been forced to compete with the non-native Menidia audens, which was introduced by waterway construction. This forced competition of resources has led to a decrease in the population of L. sicculus.

Life History

Labidesthes sicculus breed in the summer from late May to mid August. Their life span is only one year. During the first year, they have rapid growth, growing up to one milimeter per day. L. sicculus quickly reach a maximum size of approximately eight centimeters. They reach sexual maturity by the first summer in order to reproduce. Some studies report L. sicculus reproduce by internal fertilization, although this has not been entirely confirmed. When the eggs are produced, they have an attached filament . The filament allows for the eggs to be deposited on logs, plants and rocks. Temperature does not affect the sex of fish. After the eggs hatch, they immediately swim away from the short into deeper water, but still stay just under the surface . They congregate in large schools. L. sicculus migrate throughout their life cycle. No human-induced changes are reported as affecting the life history . Human-induced changes are reported as more strongly affecting populations rather than behaviors.

Current Management

Human intervention through species introduction, habitat alteration, pollution, and construction are causing the decline of L. sicculus and other freshwater fishes. Freshwater fishes account for the majority of extinctions in ray-finned fishes . To stabilize and increase populations, no more dams or waterways should be built. Additionally, pollution must be stopped. Agricultural runoff creates turbid waters, which L. sicculus can not thrive in. Stream sampling occurs through organizations such as USFWS and TVA (locally). This allows for populations to be monitored and stream chemistry to be controlled. Over-fishing and hybridization aren’t causing the populations of L. sicculus to decline. Invasive species and habitat destruction have the greatest impact on population decline. Areas are being reserved for the preservation of endemic fish, but more must still be done.

Management Recommendations

No information was found on the number of L. sicculus populations. L. sicculus is not currently listed as endangered, however, populations are declining considerably. In order to monitor the species and gain a better understanding of the population size, I would suggest stream sampling and data collection. Electroshockers would be used to shock the surface (where L. sicculus is expected to be) of the water. Downstream, sein nets would be used to collect the fish. Next, the fish collected would then be counted, reported, and released. This method would be used in many streams with varying levels of substrate concentration, temperature, vegetation, pollution, and invasive species. The habitat would need to be sampled on several occasions and during different seasons, for example, during breeding in the summer, and then again in the winter. Comparing the population densities and these varying factors would allow the determination of the most detrimental variables. The most efficient way to increase population size could then be determined. Based on previously read material, I hypothesize that both water turbidity and species introduction have the greatest affect on declining populations. If this is the case, agricultural run off should be monitored and regulated. Additionally, a program could be designed to remove invasive species which are depleting the food supply and resources. Because the main competition is a similar fish species, it would likely be very difficult to target the invasive species without affecting L. sicculus.