Performing respirometry on Nile tilapia to quanitfy specific dynamic action (SDA). Fish eat like crazy while in a tank with others, but when isolated they hardly eat (very tough to estimate meal size). Am currently collecting any food and nitrogenous waste that gets flushed from the system but this is extremely tedious and I fear quite inaccurate as a tool to work back and get an accurate meal size estimate. Have tried force feeding with gavage, but this is obviously very stressful on the fish as they need to be anaesthetized and handled and as a result the MO2 spikes drastically after force feeding (undesired).
Feeding fish is simple once you know how. Just make sure that the dry food you are using is well suited to the fish species, as described below. Once you have found a food that works well and are feeding the fish the right amount, begin supplementing their diet with insects, vegetables, or other nutritious foods depending on the type of fish.
Wish you good luck.
Hi Mark,
Try some natural feed if artificial feed is not working well in feeding. If natural feed is not feasible as per the experiment then try some taste-maker to be added in the pellet artificial feed.
If you make the feed by yourself you can add a attractive substance ( shrimp meal) to encourage the fish to eat .
Hi Mark,
I'm assuming my response is too late for the project detailed in your original question, but I am sharing this in hopes it can help you/others down the road who run into the same issue. If feed attractants, natural feed, or supplementation does not work, another thing you can try is the tube-feeding (also known as gavage) method. It is not uncommon for fish to not feed voluntarily in respirometers, as fish aren't often reared alone in a lab setting, so this is likely a stressor. To tube-feed, you will anaesthetize the fish and use a tube or forceps to administer (ideally pellets) into the stomach. This allows you to measure exactly how much food was consumed relative to the body mass of your fish. You can control for the aerobic cost of this (the increase in MR caused by elevated stress) by including a sham-fed fish (a fish that undergoes the same process as the tube-fed fish, with the exception of actual food delivery).
I currently have a manuscript under review that details this methodology if you're interested in learning more about the process:
https://www.biorxiv.org/content/10.1101/2020.07.30.229823v1
The following paper also discusses tube-feeding, and it cites other studies which have used tube-feeding in their studies as it has become fairly common:
- Chabot D, Koenker R, Farrell AP. 2016. The measurement of specific dynamic action in fishes. Journal of Fish Biology 88: 152-172.
Hope this is helpful!
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