Why Don't Your Baby Carp Survive?

December 19, 2024 0 Comments

Every year we have thousands of offspring which naturally recruit within our farm ponds. Often when working on other fisheries, fishery managers are interested to understand why silver fish reproduce so successfully but the carp don't.

Native’s vs Non-Natives

Pike, Rudd and Roach are all native species across Europe, but Carp were imported here as a food source, they're actually native to Eastern Europe an Asia. These origins of Carp generally have a slightly warmer climate, so they spawn slightly later than our native species here in the UK. This works out well for the Pike, Perch and silver species because their newly hatched fry have a perfectly timed food source once they've absorbed their yolk sacs... that being Carp eggs and tiny Carp fry!

Yolk Thieves

You can imagine, when carp fry hatch and they're relying on their egg sack to provide nutrients during their larval stages before they're developed enough for consuming food. That tiny carp fry and nutrient producing egg sac is the optimal nutrition for species that have not long finished absorbing their own yolk sac, they then benefit from the carp!

Monoculture vs Polyculture

Our fish reproduce effectively because they're reared in ponds which are drained dry annually for harvesting, so the only fish we keep in our ponds are carp - what we call a monoculture system. Therefore, they're not on the menu for any other populations like they would in a mixed fishery - polyculture system.

Clay For The Win!

Our ponds are also built from a clay substrate, clay shares its nutrients with the water far better than more coarse sediment like gravel or sand. More suspended nutrient create a far more fertile environment for fry to hatch into, a crystal clear gravel pit is quite the opposite!

Gravel and weed steals fry feed!

The sunlight penetration through the clear water of a gravel pit creates a growing environment for rooted weeds on the lakebed. These rooted weeds create habitat for predatory larvae like dragonfly larvae, damselfly, diving beetle etc. The weed not only steals nutrient from the water which are important for developing fry, but also hosts a whole new world of aquatic invertebrate life which have fish eggs and fry on the menu. However, these predatory larvae do present a food source for your mature fish, which explains why gravel pits generally produce big carp, but rarely support successful carp fry recruitment... unless sufficient water turbidity is maintained of coarse! 😁