View Full Version : Timescales for osmosis in fish cells

03/10/2017, 04:58 PM
This question is addressed to those of you who know about fish biology. I'm a mathematician, so excuse me in advance if my question is poorly phrased or my understanding of osmosis is incorrect :D. I've done some reading online but I can't seem to find any published results that answer my question. I'm curious about two things: (1) how long it typically takes for water to finish diffusing across the cell membrane in reef fish after an increase in salinity of the external sea water, and (2) how long before those cells reestablish equilibrium after that happens. Are these processes on the order of seconds? Minutes? etc.

It's more of a theoretical question for my own interest rather than for any practical value, but it sprang from thinking about the following scenario: Let's say you're trying to raise salinity while quarantining and you accidentally have a significant salinity spike (say like 3 or 4 points) due to a procedural error. If you quickly correct the salinity, will the fish's cells be "none the wiser" because osmosis occurs over a longer timescale, or will they have already adapted, in which case "correcting" the problem actually creates a second problem for them to deal with?

04/07/2017, 07:09 AM
Not going to be any help on this one but I have always read that shoreline fish can handle a rapid dip in salinity much better than a rapid spike. This would make sense to me due to heavy rains swelling creeks, streams and rivers until they suddenly dump into the coastline and slowly receed causing the salinity to instantly dip then over the course of the next few days return to normal as the fresh water stops flowing and disperses into the ocean.

When fishing coastlines we never do well after heavy rains as it is beleived fish and crab move away from the now more brackish water to deeper waters further away that have a more normal salinity.

I always take the time to measure the fish's transportation water when it arrivers then adjust the quarantine tank to match. If I already have fish in the QT then I call ahead and ask for a current reading of the tank the fish came from or the transportation water so I can gradually raise or lower the QT to match.

Interesting question though. I'd be curious to know if water diffuses across their cell membranes at different rates during rapid increases vs decreases of specific gravity.