Merrill Creek Reservoir expands fish habitat program with natural “spider blocks” built by youth corps
HARMONY TOWNSHIP, N.J. (Warren County) — A growing partnership between Merrill Creek Reservoir (MCR) and the New Jersey Youth Corps of Phillipsburg is helping expand fish habitat while reducing invasive vegetation and limiting the use of plastics in the water, officials said this week.
According to MCR, students with the Youth Corps visited the reservoir property to conduct invasive woody vegetation control and repurposed cut Autumn Olive — a non-native invasive shrub — into natural “spider blocks.” The structures are then placed in clumps or lines throughout the reservoir to create artificial reefs that offer underwater habitat for fish and other aquatic organisms.
In traditional spider block construction, PVC tubes or plastic pipes are cemented into concrete blocks to create vertical structure. MCR noted that using Autumn Olive branches instead eliminates the risk of plastics releasing chemicals or microplastics into the water over time, while still providing essential habitat for fish, macroinvertebrates and other species seeking shelter, spawning areas and foraging grounds.
Since launching the Fish Structure Creation Program in 2023, Youth Corps students have built and deployed 145 spider blocks throughout Merrill Creek Reservoir, forming multiple artificial reefs.
MCR staff filmed several of the reefs this past summer to monitor activity. Underwater footage showed the structures attracting a variety of species, including bait fish — likely Alewives — as well as Yellow Perch, Bluegill Sunfish, Black Crappie and Largemouth Bass.
