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A Very "Carpe Diem"

Mill Pond is a kettle hole lake in Southampton, NY on the South Fork of Long Island. Residents of this lake community expressed concern about the lake's water quality, including murky conditions and harmful algal blooms (HABs), which are getting worse globally with climate warming. Princeton Hydro (PH) was hired to assess factors contributing to the lake's poor water quality and determined that the lake's large population of common carp (Cyprinus carpio) likely influences the its turbidity and nutrient dynamics. Carp feeding and spawning behavior disrupts bottom sediments, which can directly influence water clarity (turbidity) and indirectly influence nutrient availability by releasing phosphorus from the sediments to the water. Once in the water, phosphorus is available for use by algae, phyotoplankton, and aquatic vegetation, causing undesirable water quality issues. We were hired to remove carp from the lake using a baited carp trap, which brought new meaning to the term Carpe Diem.

Although they look like misplaced phone poles, these rods hold the sides of our mesh trap and are fashioned with weighted triggers that can be activated from shore, capturing carp unawares.

The trap was set in a central location along the lake's peninsula, where carp could be lured to the bait. PH baited the trap with mesh bags filled with crack corn, which were placed within the trap and anchored to the bottom with bricks. The baits were set one week prior to springing the traps in order to condition a large number of fish to feed on the baits within the trap.

Cameron Swanson from Carp Solutions watches Ivy Babson and Jesse Smith fill a mesh bait sack with cracked corn to lurn carp into our trap.

After the triggering the trap from shore, we roll a large PVC boom along the underside of the netting, forcing the trapped fish into a progressively smaller area and toward an awaiting John boat.

Science! Although our mesh netting selects for adult fish, we can gain understanding of population size structure by measuring a subset of fish at each capture period. We grabbed some scales, too, to estimate age structure.

During the first capture period we collected over 1800 carp! The second capture period yielded 551 carp and the third capture period totaled 200 carp. Assuming each carp weighs a little over a pound, we removed over 3,000 lbs of carp in only three days! However, using a rough depletion model, I estimated that there are probably over a 1/2 million carp in the area influenced by our trap. We don't know exactly how large that area of influence is, but it's probably not the entire lake. This lake definitely has a carp problem! We'll be back again in the spring to make another dent in this lake's carp population and help improve Mill Pond's water quality.

Genetics! Two particular recessive alleles result in these unusual scales and patterning on this carp. Because the scales are said to resemble mirrors, this variation is called mirror carp.

Waste not... All the carp we captured were relocated to a fish tub on shore, where a local crab fisherman collected them for use as bait in his crab pots.

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