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Assessment of Dredging-Induced Sedimentation Effects on Winter Flounder (Pseudopleuronectes americanus) Hatching Success: Results of Laboratory Investigations
Citation:
BERRY, W. J., N. I. RUBINSTEIN, E. K. HINCHEY, G. KLEIN-MACPHEE, AND D. G. CLARKE. Assessment of Dredging-Induced Sedimentation Effects on Winter Flounder (Pseudopleuronectes americanus) Hatching Success: Results of Laboratory Investigations. In Proceedings, Western Dredging Association 31st Annual Western Hemisphere Dredging Technical Conference and Texas A & M 42nd Annual Dredging Seminar (WEDA 31 & TAMU 42), Nashville, TN, June 05 - 08, 2011. Texas A&M University, College Station, TX, 47-57, (2011).
Impact/Purpose:
Historically of significant commercial and recreational value, winter flounder (Pseudopleuronectes americanus) stocks have declined steadily over the last 20 years and are currently at an all-time low. Although overfishing and climate change have been implicated, habitat alteration and dredging impacts have also been identified as potential threats because winter flounder eggs are demersal (bottom oriented) and adhesive. The lack of specific information about the effects of sediment deposition on winter flounder eggs has led to the taking of a conservative approach to the protection of this species. In the present study three laboratory experiments were performed to determine the effects of sedimentation on hatching success of winter flounder. Despite variability among experiments, a trend of decreased hatching success and increased time to hatch with increasing sediment depth relative to controls was observed. Overall, these results confirm that winter flounder eggs are vulnerable to increased sediment deposition. The information coming from this study on the depth of deposition which impacts winter flounder eggs should help regulators make better-informed decisions about management practices applied to dredging operations in the vicinity of winter flounder habitat.
Description:
Historically of significant commercial and recreational value, winter flounder (Pseudopleuronectes americanus) stocks have declined steadily over the last 20 years and are currently at an all-time low. Although overfishing and climate change have been implicated, habitat alteration and dredging impacts have also been identified as sources of concern. Winter flounder eggs are demersal and adhesive. In response to a specific concern that winter flounder eggs are therefore vulnerable to elevated sedimentation rates, seasonal constraints have been imposed on many dredging projects in northeastern estuaries where winter flounder spawn. Such constraints can substantially increase the costs of dredging. Previous unpublished laboratory experiments indicated that viable hatch of winter flounder eggs can be reduced when the eggs are exposed to as little as one half of one egg diameter (~ 0.5 mm) of sediment, but these experiments were not specifically designed to measure the effects of burial. In the present study laboratory experiments were performed to determine the effects of sedimentation on hatching success. Recently spawned (3-5 days after fertilization) eggs were exposed to clean, fine-grained sediment at treatment depths including a control (no sediment), dusting (< 0.5 mm), and up to 9.3 mm (>10 egg diameters) of sediment until hatch. Despite variability among experiments, a trend of decreased hatching success and increased time to hatch with increasing sediment depth relative to controls was observed. Percent total hatch of eggs exposed to < 1.0 mm of sediment was not statistically different from that of the controls. Percent total hatch was highly variable in eggs buried in approximately 3 mm of sediment, whereas few eggs hatched successfully when buried in > 3 mm of sediment. Delayed hatch was observed in eggs buried in as little as 1 mm of sediment. Overall, these results confirm that winter flounder eggs are vulnerable to burial in sediments. These data should be taken into account whenever seasonal constraints for the protection of winter flounder are considered.