The direct and indirect effects of suction dredging on a razor clam (Ensis arcuatus) population

Robinson, Rob; Richardson, C. A.

doi:10.1006/jmsc.1998.0356

Cited by 40 publications

(20 citation statements)

References 15 publications

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“…Thus, Natural mortality of C. glaucumin Lake Timsah (M= 0.71 yr -1 ) was slightly higher than total mortality (Z = 0.24 yr -1 ). Earlier studies have shown that commercial harvesting can reduce the fitness of bivalves on intertidal areas leading to their higher mortality (Robinson and Richardson 1998).…”

Section: Discussionmentioning

confidence: 99%

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Kandeel¹,

Mohammed²,

Mostafa³

et al. 2017

Turk. J. Fish. Aquat. Sci.

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The cockle Cerastoderma glaucum represents one of the most common marine mollusc species present in Egyptian waters. This study aims to investigate the population structure, growth, mortality, and exploitation status of this cockle along Lake Qarun and Lake Timsah in order to make a comparison study. Cockles were collected from Lake Qarun at monthly intervals between February 2008 and May 2009 and collected from Lake Timsah at four seasons only. Length frequency data were analyzed using FiSAT software for estimation of population parameters to evaluate the stock. Asymptotic length (L∞) was smaller in Lake Qarun (28.35 mm) compared to that in Lake Timsah (33.60 mm).Growth coefficient (K) was higher in Lake Qarun (0.450 yr -1 ) than in Lake Timsah (0.280 yr -1 ).Growth performance index (Φ) values were similar (2.56) in both cockle stocks. The theoretical maximum age (Tmax) was higher in Lake Timsah (12.6 yr -1 ) than in Lake Qarun (7.4 yr -1 ). Total mortality (Z) was estimated by length-converted catch curve at 1.02 and 0.24 yr -1 , fishing mortality (F) at -0.04 and 0.47 yr -1 and natural mortality (M) at 1.06 and 0.71 yr -1 for Lake Qarun and Lake Timsah, respectively. Recruitment was continuous and showed two major pulses in the two lakes.

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Section: Discussionmentioning

confidence: 99%

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Kandeel¹,

Mohammed²,

Mostafa³

et al. 2017

Turk. J. Fish. Aquat. Sci.

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“…2000). Bottom-fisheries not only remove the target species (Robinson & Richardson 1998) but also impact on associated flora and fauna (de Vlas 1987b;Bergman & Hup 1992;Brylinsky, Gibson & Gordon 1994;Beukema 1995;Ferns, Rostron & Siman 2000). In addition, trawling, dredging and digging usually remove biogenic structures on the surface that are not easily replaced, such as mussel beds or banks of tube-living polychaetes, even when such elements are not the target of the fisheries (Reise 1982;Roberts 1997;Service & Magorrian 1997;Hall 1999).…”

Section: Introductionmentioning

confidence: 99%

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Piersma

Koolhaas

Dekinga

et al. 2001

Journal of Applied Ecology

166

181

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Summary1. There is world-wide concern about the effects of bottom-dredging on benthic communities in soft sediments. In autumn 1988, almost a third of the 50-km 2 intertidal system around the island of Griend in the western Dutch Wadden Sea was suction-dredged for edible cockles Cerastoderma edule and this study assessed subsequent effects. An adjacent area not directly touched by this fishery and an area from which the mussel Mytilus edulis beds were removed, served as reference areas. 2. Sediment characteristics, together with the total stock size and settlement densities of Cerastoderma , Baltic tellin Macoma balthica and soft-shelled clam Mya arenaria , were documented during 11 successive autumns before (August-September 1988) and after (August-September 1989-98) the suction-dredging event in fished and unfished areas. Four other areas in the Dutch Wadden Sea, where changes in densities of juvenile bivalves from 1992 to 1998 were measured, served as additional reference locations. 3. Between 1988 and 1994, median sediment grain size increased while silt was lost from sediments near Griend that were dredged for cockles. The initial sediment characteristics were re-attained by 1996. 4. After the removal of all Mytilus and most Cerastoderma , the abundance of Macoma declined for 8 years. From 1989 to 1998, stocks of Cerastoderma , Macoma and Mytilus did not recover to the 1988 levels, with the loss of Cerastoderma and Macoma being most pronounced in the area dredged for cockles. Declines of bivalve stocks were caused by particularly low rates of settlement in fished areas until 1996, i.e. 8 years after the dredging. 5. A comparison of settlement in the short (1992-94) and medium term (1996-98) after cockle-dredging in several fished and unfished areas spread over the entire Dutch Wadden Sea, showed a significant negative effect of dredging on subsequent settlement of Cerastoderma . Macoma also declined, but not significantly. 6. We conclude that suction-dredging of Cerastoderma had long-lasting negative effects on recruitment of bivalves, particularly the target species, in sandy parts of the Wadden Sea basin. Initially, sediment reworking by suction-dredging (especially during autumn storms) probably caused losses of fine silts. Negative feedback processes appeared to follow that prevented the accumulation of fine-grained sediments conducive to bivalve settlement.

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“…Depending on the volume of the catches, the specimens caught are sometimes only sorted at the end of the fishing day, which may decrease the survival of discarded individuals (Gaspar and Chícharo 2007). Despite the overall low mortality recorded in this study, dredging-induced stress might cause a slow recovery of the activity of discarded individuals, which thus become more vulnerable to predation (Robinson andRichardson 1998, Chícharo et al 2002b). However, several authors have reported low rates of indirect mortality in molluscs and crustaceans (Gruffydd 1972, Caddy 1973, Kaiser and Spencer 1995, the two most abundant taxa collected in the present study.…”

Section: Discussionmentioning

confidence: 86%

Bycatch and discard survival rate in a small-scale bivalve dredge fishery along the Algarve coast (southern Portugal)

et al. 2018

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Summary:Although the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for the target species, in some periods of the year the bycatch can exceed the catch of the commercial species. The present study aimed to quantify the bycatch and discards, estimate damage and mortality, and propose management measures to minimize discards and mortality. A total of 15 fishing surveys (60 tows) were performed using two types of dredges ("DDredge" targeting Donax trunculus and "SDredge" targeting Spisula solida and Chamelea gallina). Of the 85257 individuals (392.4 kg) of 52 taxa that were caught, 73.4% belonged to the target species, 22.1% to commercially undersized target species and 4.5% to bycatch species. Bycatch rates were lower for SDredge (13.5% in number and 6.3% in weight) than for DDredge (46.0% in number and 32.9% in weight). Damage and mortality rates were also lower using SDredge (1.3% and 1.0% of the total catches, respectively) than using DDredge (4.0% and 2.8% of the total catches). Survival experiments revealed the diverse vulnerability of the taxa and confirmed the influence of the damage score on the mortality rate. The results gathered in the present study encourage the adoption of a bycatch reduction device to reduce both direct and indirect mortality.Keywords: bivalve dredging; bycatch; discards; damage score; survival rate; metallic grid dredge; fishing gear technical design; bycatch reduction device Tasa de supervivencia de capturas incidentales y descartes en una pesquería a pequeña escala de bivalvos con rastro remolcado en la costa del Algarve (sur de Portugal) Resumen: Aunque la draga de bivalvos utilizada en la costa del Algarve (sur de Portugal) es altamente selectiva para las especies objetivo, en algunos períodos del año la captura incidental puede exceder la captura de las especies comerciales. En este contexto, el presente estudio tuvo como objetivo cuantificar las capturas incidentales y los descartes, estimar el daño y la mortalidad, y proponer medidas de gestión para minimizar los descartes y la mortalidad. Se realizaron un total de 15 embarques (60 arrastres) utilizando dos tipos de dragas ("DDredge" dirigida a Donax trunculus y "SDredge" dirigida a Spisula solida y Chamelea gallina). En total, se capturaron 85257 individuos (392.4 kg) pertenecientes a 52 taxones, distribuidos entre especies objetivo (73.4%), especies objetivo por debajo de la talla legal (22.1%) y especies de captura incidental (4.5%). Las tasas de captura incidental fueron menores en SDredge (13.5% número y 6.3% peso) que en DDredge (46.0% número y 32.9% peso). Las tasas de daños y mortalidad también fueron menores usando SDredge (1.3% y 1.0% de las capturas totales) que usando DDredge (4.0% y 2.8% de las capturas totales). Los experimentos de supervivencia revelaron la diferente vulnerabilidad de los taxones y confirmaron la influencia del nivel de lesiones en la tasa de mortalidad. Los resultados del presente estudio fomentan la adopción de un dispositivo de reducción de capturas inciden...

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The direct and indirect effects of suction dredging on a razor clam (Ensis arcuatus) population

Cited by 40 publications

References 15 publications

Untitled

Untitled

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Bycatch and discard survival rate in a small-scale bivalve dredge fishery along the Algarve coast (southern Portugal)

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