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| Re: Cyprinodon - high fry mortality |
Subject: Re: Cyprinodon - high fry mortality
by dkoran on 2011/12/7 18:27:36
Over 15 years of working with pupfish and hatching a few thousand eggs usually getting eggs is the hard part, however, I am trying to see where in my method I can help. Early in the game I had obtained water chemistry data for typical habitats for these fish. The biggest mistake most make is believing you add salt to the water to maintain pups - WRONG. These fish come from waters supplied by groundwater where the subsurface can still have "salts" dissolved into the groundwater. The salts you are dissolving are primarily calcium and magnesium carbonates (sodium chloride is low), your water is hard. Public water supplies try to limit hardness but if your water is on the hard side it will also be more alkaline which also will be bad for the fish. My recommendation is to develop a standard for your water, even making it up to a hardness and continue to make your water to this formulation. Also, adapt all of your breeders to this water chemistry.
I have soft water, really soft, 50-100 ppm out of the tap. I make slightly hard water, about 250 ppm. My mix for 18 gallons of water (volume of a Rubbermaid 18 gallon storage tub) consists of the following: 16.3 grams of Instant Ocean, 9.6 grams of magnesium chloride (I use a product called MAG, a hydroscopic flake used as an environmentally friendly non-sodium deicing agent)(do not use epsom salts, do not add sulfate to your water), 6.5 grams of calcium chloride (Prestone driveway heat is basically 98.5% calcium chloride), and 1.6 grams of potassium chloride (salt substitute from the grocery store works here in small quantities) and then 22 grams of sodium bicarbonate (Arm & Hammer baking sodna) but do not mix this with the other salts because water the MAG picks up will dissolve bicarb and basically generate calcium carbonate which will not dissolve readily.
It is having this consistency of water so when you add water to fry or change water you don't shock the fry. Without this consistency you have the potential of having osmotic shock on the developing gills of the fry.
Second, consider temperature - since I was usually breeding the pups at ambient temperature this meant no heaters in the tank so your eggs were incubating at ambient temperature and then growing in rearing containers at ambient temperature - hence during the normal breeding season I would breed the pups from June 'til September in my "greenhouse". In the past I noticed that fry hatched and reared indoors at a constant temperature tended to have lower survivability. For some reason I believe the fluctuation in diurnal temperatures for the first 2-3 months of the young fish life tended to "toughen" them and make them healthier.
This is probably one reason that most people who atempt to work with pups eventually settle on the "natural" method and succeed by basic recruitment.
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