Pond Boss
Posted By: azteca 2 questions for Mr Cody. - 04/11/21 02:00 PM
Hello.

Is it possible that the perch eggs that we see floating on the water, are mostly unfertilized eggs.

I think there is a controversy concerning Copepodes (Cyclops), especially among aquarium owners to the effect that Cyclops can be predatory of very small larvae of fish.
What do you think.
A+
Posted By: Bill Cody Re: 2 questions for Mr Cody. - 04/11/21 10:22 PM
Floating perch eggs. I think ribbons of perch eggs have a tendency to float when they are dipped out of the water and get air mixed within or into the ribbon. The ribbons are hollow. Air in the ribbon tends to make the ribbon more likely to float. Rising gases produced within the pond could also get trapped in the ribbon and cause it to float. I am not sure that unfertilized and dead, dying eggs would produce enough gas to float a ribbon - maybe? Best way to check for unfertilized eggs is the individual eggs will turn opaque, noticeably white a few days after it is laid when eggs are dead-unfertilized.

"...controversy concerning Copepodes (Cyclops), especially among aquarium owners to the effect that Cyclops can be predatory of very small larvae of fish". Some of the large common pond Copepods are considered predatory but IMO the predation actually best described as food selectivity in freshwater and marine studies has typically been on items a lot smaller than a fish fry; things mostly such as small forms of algae and maybe tiny protozoa. (See below).

Most common pond dwelling Copepods mainly Cyclops and Mesocyclops are generally small in the size length range of 0.9-1.3mm. Yellow perch eggs range in diameter of 2 to 4.5 mm depending on the amount or degree of egg water hardening. Body length of newly hatched YP fry ranges from 5.5 to 6.5mm. I doubt that the common pond Cyclops species could ever attack and eat something 4 times larger than themselves. Swim up perch fry could easily swim much faster than swimming adult Copepods so IMO the chances of common pond Copepods eating YP fry is not possible. Yellow perch fry commonly feed on the nauplii (baby Copepods) and rotifers. Perch fry after several days eat lots of adult Copepods. I think adult Copepods are much more likely to eat newly hatched 'baby' Copepods(nauplii 0.22-0.25mm) than yellow perch fry. Although I think nauplii are likely still too big for adult Copepods to eat. Tiny algae cells range in size from 2um to 20um(0.002-0.02mm).

Not a lot of research has been done about the feeding habits of small, tiny Copepods who have shown some ability to exhibit feeding selectivity. Research has shown that this selectivity is primarily based on eating algae with factors such as size, motility and taxonomic composition are considered the major items controlling the feeding selectivity of copepods. It is generally assumed that small copepods, including nauplii, feed primarily upon small-sized phytoplankton and including even organic detritus pieces. This is general info from Wikipedia – “Most free-living copepods feed directly on phytoplankton, catching cells individually. " (Note- "Catching cells individually" is probably how the term predation by Copepoda originated.) "A single copepod can consume up to 373,000 phytoplankton per day.[12] They generally have to clear (or search) the equivalent to about a million times their own body volume of water every day to cover their nutritional needs.[13] Some of the larger Copepod species are predators of their smaller relatives.”
Posted By: Theo Gallus Re: 2 questions for Mr Cody. - 04/12/21 11:03 AM
Right there is more than I knew I needed to know about Copepods. Thanks, Bill.
Posted By: azteca Re: 2 questions for Mr Cody. - 04/12/21 03:35 PM
Hello.

Thank you Mr. Cody.
I was wondering because there are a lot of Cyclops in the pond this spring.

A+
© Pond Boss Forum