Development of Bubble Screen Deterrents for Controlling Movements of Invasive Carp Eggs and Larvae in Streams
Advisor: Prof. Rafael O. Tinoco
Date: Thursday Oct 31st, 2024, 10:30 am CDT
Location: CEEB 3012 (Conference Room)
Zoom link:
https://illinois.zoom.us/j/84945701066?pwd=TaEDNX6XGqfhbNdJ8EhTlCHV4BvNiL.1
Meeting ID: 849 4570 1066
Password: 872593
Abstract
This study proposes a novel application of oblique bubble screens (OBS) as a potential
deterrent for downstream drifting eggs and larvae of invasive carp. The study is divided in
four stages: (1) initial characterization of particle-OBS interactions, (2) assessment of OBS
effect on live grass carp eggs and larvae, (3) characterization of surrogates to accurately
mimic live egg response, and (4) refining of OBS design for increased capture efficacy.
1. The efficacy of various OBS configurations at redirecting downstream drifting particles
was initially tested with fish egg surrogates of a wide range of physical properties, including
negatively buoyant (NB), positively buoyant (PB) and semi-buoyant (SB) particles. The
OBS could successfully redirect PB, NB and SB to pre-determined target locations for their
capture. The redirection was facilitated by the OBS-induced lateral push, characterized
through detailed hydrodynamic measurements around the OBS. The effects of airflow rate,
mean flow velocity and inclination angle of the diffusers on the redirection efficiency were
investigated.
2. Selected OBS configurations were used to assess redirection of live eggs and larvae
at different developmental stages, from pre- to post-gas bladder inflation (GBI). The study
showed lower egg capture rates than NB, PB, and SB particles, primarily due to nearly
neutrally buoyant behavior of the eggs which lead to inconsistent responses to the recirculation
induced by the OBS. The studies with live larvae revealed an active response from
post-GBI larvae, particularly at low flow velocities. The hydrodynamic study allowed us to
identify large-scale OBS-generated motions as the drivers of the spatial distribution patterns
observed for eggs, pre-GBI larvae, post-GBI larvae, and dead larvae.
3. To overcome the limitations of using live grass carp eggs in laboratory experiments
(e.g., their seasonal availability which limits year-round access, their 1-day hatching time
1
which limits the number of experimental conditions which can be tested during the egg
stage, and their fragility, which limits the flow conditions and handling required to avoid
ruptured membranes), we developed surrogates to closely replicate live carp egg movement.
Plastic beads with adjusted weights and formalin-preserved eggs were tested in settling
column experiments and used to study the efficacy of a broad range of OBS configurations
to confirm the surrogates’ ability to closely mimic the behavior of grass carp eggs in a highly
turbulent environment.
4. Given low capture rates of eggs with OBS configurations, the approach was modified by
placing the diffuser parallel to the mean flow aligned with the flume centerline and aiming for
capturing particles along the flume walls. The modified approach generated helical motions
which yielded a high capture efficiency. Five different grass carp life stages were tested: live
eggs, pre-GBI larvae, post-GBI larvae, dead larvae and eggs preserved in formalin. Capture
efficacy remained consistent across all stages and was determined to be a function of airflow
rate for a given flow speed. Compared to lower velocities, achieving equivalent capture
efficacy at higher flow velocities required increased airflow rates and an extended side net
coverage. We defined a timescale associated with one recirculation of the helical motion and
estimated the effective length of the target nets to achieve a given capture rate.
The study showed the potential of oblique bubble screens (OBS) as a novel tool for controlling
the spread of invasive carp in streams. By strategically modifying the hydrodynamic
field, OBS can effectively redirect and capture drifting eggs and larvae, offering a promising
approach for mitigating the ecological impact of invasive species. This technology can be
fine-tuned to target specific fish species based on their physical properties, allowing it to be
implemented in various aquatic environments to help protect native ecosystems and biodiversity.