Department of Forest Sciences
3041-2424 Main Mall, UBC
Vancouver, B.C. V6T 1Z4
Position: Ph.D. Candidate
Study Area: Ontogenetic effects of the signal crayfish within stream food webs.
HI! I’m Carin Bondar, a PhD student in the Richardson lab. I’m currently knee deep in samples and data…and looking forward to many hours of bug picking in the next few seasons. I’m also off to New Zealand in January 2004 to complete a comparative study on the ecology of juvenile crayfish (which began in Summer 2003 in Malcolm Knapp Research Forest).
I’ve always been interested in the process of development. For my masters degree I looked at the evolution of gastropod developmental programmes through a detailed study on two caenogastropod species (check it out in Invertebrate Biology 122(1): 28-41). I’m still very much interested in the developmental process, and my PhD work largely encompasses the ecological differences that may arise when an organism develops through several distinct stages. Here’s a quick synopsis of my current projects and interests…feel free to contact me if you’d like more information!
Current Project: In order to adequately assess the total impact of an organism on its environment, one must consider the possibility that the organism may have different ecological roles through its development. Most fish, amphibians, and invertebrates undergo distinct ontogenetic niche shifts, changes in resource or habitat use related to size or developmental stage, which may render different life history stages of the same organism functionally different contributors to the ecosystem. Species that develop over a large size range (in some cases up to 5 orders of magnitude) will have a wider use of resources, and more potential to vary ontogenetically in niche requirements than species that change little in size through development. Ontogenetic niche shifts can vastly complicate species interactions and have important consequences for community dynamics.
Arthropods, such as decapod crustaceans, have been recognized as playing important roles in structuring freshwater communities. Such organisms may undergo vast size changes through development. For example, adult freshwater crayfish may attain sizes as large as 50g while young of the year crayfish may weigh as little as .1g. In addition to these biomass differences, crayfish have repeatedly been shown to undergo distinct ontogenetic niche shifts with respect to food and habitat choice. Juveniles are predatory and prefer shallow areas of streams, whereas adults are primarily omnivorous and are most often found in deep pools.
Several researchers have clearly shown that adult crayfish have the capability of structuring both lotic and lentic freshwater ecosystems through keystone predation and indirect effects. However, few researchers have attempted to assess the ecological roles of other ontogenetic stages of this important member of the benthic community. The principal objective of my research is to elucidate the ecological roles of several ontogenetic stages of the signal crayfish, Pacifastacus leniusculus in a small temperate stream ecosystem.
I have been able to accomplish several major experiments on this subject during my first two field seasons. In the summer of 2002 I completed a large-scale enclosure experiment in Malcolm Knapp Research Forest (located in Maple Ridge, British Columbia), in which I regulated density and ontogenetic stage of crayfish within 1 m2 enclosures (45 enclosures in total). The enclosures were constructed from PVC piping and hardware cloth (mesh size 1cm2), and did not allow for either immigration or emigration of crayfish with a carapace length >20mm (which coincides with an age of 2+ juveniles). The results from this experiment show some interesting patterns, which will be submitted for publication later this semester. During the summer of 2003 I was able to replicate the large-scale enclosure experiment, this time incorporating the ontogenetic interactions between crayfish and another predator in the stream system, the cut-throat trout. In addition to this experiment, a smaller-scale enclosure experiment contrasted the ecological role of young of the year crayfish with 3+ crayfish, and several capture-mark-recapture surveys allowed for a more detailed look at crayfish population size and size-structure in small streams. Future field experiments will expand on these studies, most immediately to replicate the capture-mark-recapture research in several other lotic and lentic environments.
To accompany the data from the field experiments, I have completed two laboratory studies. The first involved monitoring the growth rate of adult and juvenile crayfish on different food media. The second was a food choice study in which adult and juvenile crayfish were tested for their preference between the food types used in the growth experiment. These laboratory experiments were undertaken to follow up on some unexpected results from the 2002 experiment. The data show that several ontogenetic stages of crayfish are dependent on detrital food sources for the majority of their diet, which may have important implications for the conservation of riparian areas adjacent to small streams.
Pacifastacus leniusculus is currently classified by World Wildlife Fund Canada as vulnerable: likely to become at risk because of naturally low or declining numbers or a small range. It has been postulated that the vulnerable status of crayfish in British Columbia stems from their susceptibility to anthropogenic disturbance and habitat destruction, and my results to date support this assertion. Understanding the overall role of this organism in stream ecosystems is therefore of growing importance to both conservation biologists and environmental managers.