Other Possible Stressors

Pesticide Application, Toxic Substances, and Chemical Spills

All mosquitocides registered for use in Florida, when applied properly and in recommended concentrations, pose no known threats to water quality. The Bay County Mosquito Control District uses state-registered insecticides to treat both larval and adult mosquitoes. Only larvicides are applied directly to waters that may be inhabited by the PCC. The Bay County Mosquito Control District utilizes two larvicides, S-methoprene and Bacillus thuringiensis israelensis (Bay County Mosquito Control Division, personal communication, 2007).

Many substances commonly used around the home or business can be toxic to PCC and other wildlife if used or disposed of improperly. Since PCC often inhabit ditches and swales close or adjacent to private properties, landowners need to ensure that fertilizers, insecticides, and herbicides are applied and disposed of per label directions. Potentially toxic substances such as petroleum products and paint should be properly disposed of at hazardous waste disposal facilities. Accidental spills of large volumes of toxic substances such as petroleum products and acids occasionally occur in urban areas. If spills overflow into ditches, swales, or other areas inhabited by PCC, substantial localized impacts to the population are possible. Ditching and draining urban areas is a common practice in efforts to control local flooding events and reduce mosquito outbreaks but could have accidental impacts, especially to populations with small amounts of available habitats by artificially draining or decreasing the amount of time that surface waters are available.

Batteries of all types should be disposed of at hazardous waste disposal facilities. Outreach efforts to remind landowners near PCC occupied sites how to safeguard downstream wildlife will be important to PCC conservation in the future. Accidental spills of toxic substances should be contained and neutralized as soon as possible to minimize damage to the PCC and other wildlife populations.

Disease

Disease agents and pests identified for freshwater crayfish include viruses, bacteria, rickettsia-like organisms, fungi, protistans, and metazoans (Evans et al. 2002, p. 1). The red swamp crayfish (Procambarus clarkii), has been introduced into many countries and into portions of the United States outside its native range. In many areas, it has had severe impacts on native crayfish, either by direct competition or through the spread of crayfish plague (Longshaw and Stebbing 2016; p. 16). Crayfish plague is a water mold that infects crayfish, which may die within weeks after contact. We have no knowledge of localized populations of P.clarkii nor crayfish plague. However, detailed information on most disease agents, disease conditions, and symbiont associations is lacking (Evans et al. 2002, p. 3), and there is no reported information on the presence of disease or parasites in the PCC to date. Several individuals of Procambarus apalachicolae, a sister species in near proximity to the PCC, have exhibited signs of plague-like infection (Paul Moler, FWC, personal communication, June 23, 2017).

Off-road Vehicle Use

Off-road vehicles can adversely impact PCC. Indirect effects include altering local hydrology by rutting and breaking the hardpan, decreasing water quality, and reducing vegetation. ORV use is primarily a concern in the eastern portion of the range, specifically within Gulf Power right-of-way corridors. When problems have been identified, Gulf Power personnel have constructed gates to block access, thereby currently limiting public access to their lands for this form of recreation.

Illegal Harvest and Overutilization

Overutilization is a potential threat to imperiled species. In particular, the threat to crayfish species from overutilization is from the collection of individuals for bait or food. Harvesting PCC for fish bait or other uses may have long-term effects on populations if large numbers of adults are taken from single or adjacent locations. Several occurrence points in the range of the PCC are locally known as good sites to acquire crayfish for fish bait. Harvesting crayfish at those sites has been documented, but the magnitude of the impacts of recreational harvest on the PCC is unknown (Keppner and Keppner 2001, 2005).

The species and its habitats are not known to be targeted for significant scientific or educational collections. Florida State Code 68A-9.002 authorizes the Director of the Florida Fish and Wildlife Conservation Commission to issue permits to collect any wildlife species for scientific or conservation purposes, which are required for activities that are otherwise prohibited.

Direct Competition with and Predation by Other Species

Nothing indicates that predation or competition by native or non-native predators is currently affecting PCC. Range expansion by two other crayfish species inhabiting the eastern (P. kilbyi) and northern (P. apalachicolae) boundaries of the PCC range could cause local displacement of the PCC along these boundaries, thereby reducing the number of PCC. These two species are superficially identical to PCC, but can be distinguished by close examination of the male reproductive structures. Some P. kilbyi and P. hubbelli have been recently found in small areas of the PCC range.

The introduction of nonindigenous crayfish for bait purposes has contributed to declines of native crayfish populations in other areas (Holdich 1987, Hobbs et al. 1989). Introduced crayfish species, such as those of the genus Cherax (now present in Alabama), may outcompete native crayfish and thereby reduce the number of PCC (Keppner and Keppner 2001, 2005; F. Bingham, personal communication).

Inadequate Regulatory Mechanisms

The level of protection for the PCC is not expected to be reduced in the future and may increase. The species is currently listed as a Species of Special concern in Florida. The FWC has been petitioned to list the species as a Threatened Species, but that listing action is contingent upon finalization of the management plan (FWC 2016). The FWC has indicated that the current level of monitoring, including species distribution and population monitoring, will likely increase, as will management actions (FWC 2017; Steve Shea and Melissa Tucker, personal communication, June 16, 2017). Management actions proposed in the draft management plan include population management, such as translocation and augmentation, as well as mitigation for habitat impacts. The FWC has worked in close coordination with the Service and plans to integrate the latest population and genetic work (Duncan et al. 2017) in subsequent revisions of the management plan (Steve Shea and Melissa Tucker, FWC, personal communication, June 16, 2017).