Crayfish in the back lakes.

Posted by Sarah M. Larocque and Mark A. Conboy

Figure 1. A) Dorsal and B) ventral view of a calico crayfish (Orconectes immunis) found in Lindsey Lake.

In a recent blog post (November 11), we reported our results of the small fish community survey undertaken in the QUBS back lakes and wetlands this summer. In addition to gathering information on fish, we took advantage of our time on the water to sample crayfish diversity at each water body. We captured crayfish using baited minnow traps and seine nets as outlined in the fish post. In this post we also included crayfish data from Lake Opinicon (which we did not sample in the fish survey). Specimens from Lake Opinicon were caught using minnow traps, seine nets and by hand. Crayfish are yet another group of organisms that have received virtually no attention at QUBS; we present the first (preliminary) summary of crayfish diversity and distribution for the station.

Understanding the diversity and distribution of crayfish at QUBS is important for three reasons. First, we would like to provide distributional information to future crayfish researchers who may be looking for study populations. Second, we want to compare contemporary species distribution to future sampling results in order to understand the changes that take place in lake and wetland ecology over time. Finally, crayfish, though often abundant in healthy ecosystems can quickly become imperiled through pollution and the introduction of invasive species. Crayfish are the largest mobile invertebrates in Ontario, and play an important role as scavengers, predators and prey in our aquatic ecosystems. We want to be able to monitor the health of QUBS’s crayfish populations to ensure their continued vitality and the vitality of our aquatic ecosystems at large.

Worldwide there are more than 540 species of crayfish (also called crawfish or crawdads). Crayfish diversity in Canada is low with only 11 species, all of which, except for the Signal Crayfish (Pacifastacus leniusculus), are found in Ontario. The centre of crayfish diversity in the province is southwestern Ontario, but at least five native and two introduced species of crayfish may be found at or near QUBS. Our sampling turned up four species:

  • Virile Crayfish (Orconectes virilis) –  Very common in Lake Opinicon and Warner Lake
  • Calico Crayfish (O. immunis) – Fairly common in Lake Opinicon, Warner Lake, Round Lake, Lindsey Lake, Cold Springs Pond and Lower Poole Pond. Abundant in the Dowsley Ponds.
  • Northern Clearwater Crayfish (O. propinquus) – Appears to be fairly common at Chaffey’s Lock and other locations in Lake Opinicon. Found in some wetlands along Cataraqui Trail. Not yet recorded in the back lakes.
  • Common Crayfish (Cambarus bartonii) – One collected at Warner Lake; first record for this species at QUBS. Could also be found in streams but has not been to date.

An additional native species reaches eastern Ontario but it prefers large rivers, a habitat type which is lacking at QUBS, so it is unlikely to be found at the station. Fortunately, no invasive crayfish species have been found at QUBS. There are two invasive species of concern in eastern Ontario Rusty Crayfish (O. rusticus) and Allegheny Crayfish (O. obscurus). The spread of these invasive crayfish is due in large part to transportation from their native ranges to other watersheds by anglers who use them as bait. The introduction of the Rusty Crayfish in Ontario took place in 1960’s when it was brought here for use as bait by a non-resident angler. To help stop the spread of invasive crayfish it is currently illegal in Ontario to transport crayfish (dead or alive) to water bodies other than where it was caught. Also, if you think you caught an invasive crayfish, you are supposed to kill it and report the observation to the Ministry of Natural Resources. However, it is important to identify crayfish correctly before killing them. An excellent visual guide to all of Ontario’s crayfishes can be found here.

Some native crayfish (e.g., Northern Clearwater) are in decline due to competition for food and shelter from the dominant and more aggressive Rusty Crayfish. Recently an article published in Fisheries (Lieb et al. 2011) explores various management strategies to prevent the spread of invasive crayfish spread and conserve threatened native crayfishes in North America. Restrictions on transport of bait and education can be effective tools to prevent the further spread of invasive species but once non-native crayfish become established it can be almost impossible to remove them. As we expand our sampling of lakes and wetlands at QUBS this coming summer we’ll continue to document the native and non-native crayfish and work towards monitoring our local water bodies for the first signs of invasion by invasive species so that we can act quickly to ensure the integrity of our native crayfish diversity.

Lieb DA, Bouchard RW, Carline RF, Nuttall TR, Wallace JR, Burkholder CL. 2011. Conservation and management of crayfishes: Lessons from Pennsylvania. Fisheries 36: 489-507

Figure 1. A) Dorsal and B) ventral view of a calico crayfish (Orconectes immunis) found in Lindsey Lake.