Impacts of electrofishing for razor clams (Ensis spp.) on benthic fauna

Murray, Fiona; Copland, Philip; Boulcott, Philip; Robertson, M. R.; Bailey, N.

doi:10.1016/j.fishres.2015.08.028

Cited by 17 publications

(17 citation statements)

References 25 publications

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“…SumWing trawling reduced the seabed roughness the most as tickler chains are towed in perpendicular direction to the towing direction and flatten the seabed across the trawl track ( Figure 5). PulseWing trawling reduced BS less as the shallow indentations by the electrodes are caused in parallel direction to the towing direction (Murray et al, 2016).…”

Section: Seabed Topographymentioning

confidence: 99%

Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl

Depestele¹,

Degrendele

Esmaeili

et al. 2018

ICES Journal of Marine Science

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Tickler-chain SumWing and electrode-fitted PulseWing trawls were compared to assess seabed impacts. Multi-beam echo sounder (MBES) bathymetry confirmed that the SumWing trawl tracks were consistently and uniformly deepened to 1.5 cm depth in contrast to 0.7 cm following PulseWing trawling. MBES backscatter strength analysis showed that SumWing trawls (3.11 dB) flattened seabed roughness significantly more than PulseWing trawls (2.37 dB). Sediment Profile Imagery (SPI) showed that SumWing trawls (mean, SD) homogenised the sediment deeper (3.4 cm, 0.9 cm) and removed more of the oxidised layer than PulseWing trawls (1 cm, 0.8 cm). The reduced PulseWing trawling impacts allowed a faster re-establishment of the oxidised layer and micro-topography. Particle size analysis suggested that SumWing trawls injected finer particles into the deeper sediment layers (∼4 cm depth), while PulseWing trawling only caused coarsening of the top layers (winnowing effect). Total penetration depth (mean, SD) of the SumWing trawls (4.1 cm, 0.9 cm) and PulseWing trawls (1.8 cm, 0.8 cm) was estimated by the depth of the disturbance layer and the layer of mobilized sediment (SumWing = 0.7 cm; PulseWing trawl = 0.8 cm). PulseWing trawls reduced most of the mechanical seabed impacts compared to SumWing trawls for this substrate and area characteristics.

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Section: Seabed Topographymentioning

confidence: 99%

Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl

Depestele¹,

Degrendele

Esmaeili

et al. 2018

ICES Journal of Marine Science

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“…In fact, these deep-water sediments are particularly sensitive to trawling disturbances, a concerning feature given the steady expansion of fishing practices into deeper waters in recent decades (Morato et al, 2006;Puig et al, 2012;Watson and Morato, 2013). Deep-water species communities are slow growing and thus recover slowly, organic matter deposition rates are low, and the generally finer grained sediments found in the deep are easily resuspended following a trawl passage (Norse et al, 2012;Mengual et al, 2016). All three of these factors increase the impacts of trawling events on organic matter cycling in the model presented in this work, and further modelling work could be useful to investigate the potentially large impact that deep-sea habitat experience.…”

Section: Organic Carbon Depletionmentioning

confidence: 99%

Impact of bottom trawling on sediment biogeochemistry: a modelling approach

et al. 2021

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Abstract. Bottom trawling in shelf seas can occur more than 10 times per year for a given location. This affects the benthic metabolism, through a mortality of the macrofauna, resuspension of organic matter from the sediment, and alterations of the physical sediment structure. However, the trawling impacts on organic carbon mineralization and associated processes are not well known. Using a modelling approach, the effects of increasing trawling frequencies on early diagenesis were studied in five different sedimentary environments, simulating the effects of a deeper-penetrating gear (e.g. a tickler chain beam trawl) versus a shallower, more variable penetrating gear (e.g. an electric pulse trawl). Trawling events strongly increased oxygen and nitrate concentrations in surface sediment layers and led to significantly lower amounts of ammonium (43 %–99 % reduction) and organic carbon in the top 10 cm of the sediment (62 %–96 % reduction). As a result, total mineralization rates in the sediment were decreased by up to 28 %. The effect on different mineralization processes differed both between sediment types and between trawling frequencies. The shallow-penetrating gear had a slightly smaller effect on benthic denitrification than the deeper-penetrating gear, but there were no statistically different results between gear types for all other parameters. Denitrification was reduced by 69 % in a fine sandy sediment, whereas nitrogen removal nearly doubled in a highly eutrophic mud. This suggests that even relatively low penetration depths from bottom fishing gears generate significant biogeochemical alterations. Physical organic carbon removal through trawl-induced resuspension of sediments, exacerbated by a removal of bioturbating macrofauna, was identified as the main cause of the changes in the mineralization process.

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“…Compared with the control groups, there were significant reductions in the survival rate of exposed king ragworm Allita virens and European green crab Carcinus maenas of 3% and 5%, respectively, when all exposures were clustered by species regardless of the distance from the electrode. Atlantic razor clams Ensis directus exhibited a significant 7% reduction in IMPACT OF ELECTRICAL AND MECHANICAL STIMULATION ON BROWN SHRIMP 405 survival rate at 0.1 m from the electrodes but a greater survival rate at 0.2 m. The latter result is odd, since Murray et al (2016) did not find an impact on the survival of the razor clam Ensis siliqua exposed in both laboratory and field trials to nonpulsed alternating current. Furthermore, food intake was significantly reduced by 10-13% in the European green crab.…”

mentioning

confidence: 90%

Laboratory Study of the Impact of Repetitive Electrical and Mechanical Stimulation on Brown Shrimp Crangon crangon

Soetaert

Verschueren²,

Chiers

et al. 2016

Mar Coast Fish

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Pulse trawling is currently the best available alternative to beam trawling in the brown shrimp Crangon crangon and Sole Solea solea (also known as Solea vulgaris) fisheries. To evaluate the effect of repetitive exposure to electrical fields, brown shrimp were exposed to the commercial electrodes and pulse settings used to catch brown shrimp (shrimp startle pulse) or Sole (Sole cramp pulse) 20 times in 4 d and monitored for up to 14 d after the first exposure. Survival, egg loss, molting, and the degree of intranuclear bacilliform virus (IBV) infection were evaluated and compared with those in stressed but not electrically exposed (procedural control) and nonstressed, nonexposed (control) brown shrimp as well as brown shrimp exposed to mechanical stimuli. The lowest survival at 14 d (57.3%) occurred in the Sole cramp pulse treatment, and this was significantly lower than in the group with the highest survival, the procedural control (70.3%). No effect of electrical stimulation on the severity of IBV infection was found. The lowest percentage of molts occurred in the repetitive mechanical stimulation treatment (14.0%), and this was significantly lower than in the group with the highest percentage of molts, the procedural control (21.7%). Additionally, the mechanically stimulated brown shrimp that died during the experiment had a significantly larger size than the surviving individuals. Finally, no effect of the shrimp startle pulse was found. Therefore, it can be concluded that repetitive exposure to a cramp stimulus and mechanical stimulation may have negative effects on the growth and/or survival of brown shrimp. However, there is no evidence that electrical stimulation during electrotrawls would have a larger negative impact on brown shrimp stocks than mechanical stimulation during conventional beam trawling.Received November 15, 2015; accepted May 16, 2016

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Impacts of electrofishing for razor clams (Ensis spp.) on benthic fauna

Cited by 17 publications

References 25 publications

Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl

Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl

Impact of bottom trawling on sediment biogeochemistry: a modelling approach

Laboratory Study of the Impact of Repetitive Electrical and Mechanical Stimulation on Brown Shrimp Crangon crangon

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