I am examining stomach contents of a large piscivore in British Columbia, and the four expected prey species are mountain whitefish, juvenile sockeye salmon, juvenile bull trout, and juvenile rainbow trout (all under 150 mm FL). I have a good resource for dentary, cranial, and otolith bones to differentiate between mountain whitefish and sockeye salmon. However, I do not have a key that includes bull trout or rainbow trout, especially in comparison to sockeye (we are interested in how much sockeye salmon are in the diet, and thus don't care about differentiating among the other species as much).
Any tips or references would be greatly appreciated; thank you for your time.
Use the jaw bones....i had succes with that differentiating highly similar cyprinid fish species
Hey Nathan,
Why not to use otholits for all species? there should be differences between all those species, and it is good for individuals counting (one pair of otoliths (left and right) = one fish), because otoliths remain undigested. actually they are pretty small for such size fishes, but I think it is one of the best ways :)
Regards, Justas
You might have troubles with rainbow trouts as many wild populations are now hybrids, not "pure" species anymore.
Nathan,
Although it will require more work, your best bet might be to procure specimens of each species and skeletonize them yourself and examine them for potential differences in several different skeletal elements, as you state that you already have for the whitefish and salmon. If you have several elements to choose from you run a better chance of being able to identify more remains as the same elements may not be available for all stomachs.
Supraetmoid shape is variable among salmonid fish and can serve as an identification feature. We have successfully differentiated juvenile Pacific salmon species in mixed catches by this feature. In English, see Vladykov, V.D. Osteological Studies on Pacific Salmon of the Genus Oncorhynchus. Fisheries Research Board of Canada Bull, No. 136. Ottawa: 1962. 172 pp.
Thanks for the thoughts everyone.
@ Justas - I am alright using otoliths for everything (although dentary bones are very distinct between sockeye and mountain whitefish), but I need to know what otoliths look like for rainbow trout and bull trout and how they can identified from sockeye (Christian's suggestion would solve this issue, but I was hoping not to get extra permitting to try to catch representative live samples, especially if resources are already available).
Vladamir, could you point me towards the reference you found? I am unable to find it, either through my library or even on the DFO website.
Hopefully others will continue to post. Even if anyone knew of high-quality photos of otoliths and/or cranial bones of these species (bull trout, rainbow trout) that would be really helpful.
Nathan, try this reference:
http://www.dfo-mpo.gc.ca/Library/10037.pdf
Impressive paper of Vladykov. However, no rainbow/steelhead and no bull trout there, especially when juveniles. I agree with Christian, the skeltozied juveniles will serbve the best for your task, as it served when one of my students worked out the feeding habits of the kingfisher. I am aware that maybe the bull trout samples will be difficult to get, but the full set of bones will cover the majority of comparisons (of which some might contain only a limited extent of bones in the gut content). It seems this harder way is the best one.
Hi Nathan, do you want to learn to ID the bones yourself or have someone else do it? If it's the latter, the Marine Mammal Research Unit at UBC used to identify marine fish bones from pinniped scat. (I had the enviable summer job of collecting scat and separating the bones!) I think someone on Vancouver Island actually identified the bones, maybe in Victoria or Nanaimo. You could contact Prof. Andrew Trites at the MMRU for more information. Hope that helps, good luck.
Hi Nathan,
Contact Shayne MacLellan, who runs the Sclerochronology Lab or aka the fish-ageing lab at DFO's Pacific Biological Station (PBS) in Nanaimo, BC. She is extraordinary knowledgeable and should be able to direct you to appropriate lit and might have some good tips for you in distinguishing them.
Hey Nathan,
An expert on fish bones that may have the reference specimens you are in need of is Dr. Kenneth Gobalet at California State University - Bakersfield. Good luck.
Thank you everyone for the great responses. While I will keep searching for more sources, I am certainly farther along than I was previously. I know have photos/drawings of at least a single otolith from all species. I will still try to acquire more, as well as potentially some actual samples for comparison.
Pamela, I would like to especially thank you, as the Sclerochronology Lab has been a great help!
Aerin, thank you for your suggestion as well; I am quite familiar with Dr. Trites' work and respect his research quite a bit. Unfortunately (for me), his pinnipeds eat mostly marine fishes.
Vladamir - thank you for the reference!
Predrag and Christian - I agree that having the representative skeletal samples would be ideal, and am exploring options for obtaining these samples (still many challenges of doing this in the system we are working)
Jereme - thank you, I will contact Dr. Gobalet soon!
Alwynne and Yolanda - thank you for your kind input! Alwynne, your suggestion in particular was extremely helpful, as Dr. Driver pointed me in the direction of some colleagues who have been extremely helpful. Through everyone's suggestions, I have been able to collect a variety of photos of otoliths and other bones for my potential species, as well as access to a fish bone collection to make direct comparisons, as well as some expert help/training to get me started!
This really demonstrates ResearchGate's incredible potential to positively impact science, and thank you all again for making that possible.
I'm going to go out on a limb here and see if you cant try a molecular approach. If you used real time pcr you might be able to munch up the bones and identify contributing species based on species specific markers.
It would be fast, but pretty expensive.
Just a thought.
Thank you for the response Culum. We are considering using a molecular approach in the future (if funding permits) but on these samples we simply don't have the budget required for the approach and thus require a more laborious process. These samples represent pilot work collected while conducting work.
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