Implications of the effects of trawling on sessile megazoobenthos on a tropical shelf in northeastern Australia

Pitcher, C. Roland; Poiner, I. R.; Hill, B. J.; Burridge, Charis Y.

doi:10.1006/jmsc.2000.0911

Cited by 71 publications

(56 citation statements)

References 13 publications

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“…Highest intensity of fishing was concentrated on small seamounts on the south Chatham Rise. Most previous attempts to quantify the spatial intensity of trawling estimated trawl effort in a grid of cells over the fishing grounds (e.g., Piet et al 2000;Pitcher et al 2000;Cranfield et al 2003). The choice of grid cell size is important because fishing effort is seldom homogeneously distributed over a wide area.…”

Section: Discussionmentioning

confidence: 99%

“…Even a small number of tows may lead to significant impact. For example, Pitcher et al (2000) reported that each tow removed roughly 5-20% of the available biomass of sessile epibenthos on the Great Barrier Reef. A single trawl can sweep the sea floor over a width of 100-200 m (doorspread), and on a small seamount the threshold level of five tows in a given direction may represent a significant fraction of the total seabed area.…”

Section: Discussionmentioning

confidence: 99%

“…Other studies have shown that the type of bottom trawl gear used in New Zealand seamount fisheries has a marked impact on the bottom, with removal of benthic fauna (Probert et al 1997;Koslow et al 2001). However, the impact will depend on substrate type and community composition, as well as intensity of fishing (van Dolah et al 1987;Freese et al 1999;Pitcher et al 2000). The coral cover present on many seamounts is fragile, and easily damaged by bottom trawl gear (Clark & O'Driscoll 2003), whereas the same intensity of trawling may have a smaller impact on a softer substrate (e.g., Sanchez et al 2000).…”

Section: Discussionmentioning

confidence: 99%

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Quantifying the relative intensity of fishing on New Zealand seamounts

O’Driscoll

Clark

2005

New Zealand Journal of Marine and Freshwater Research

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New Zealand seamounts support major fisheries for several deepwater fish species, including orange roughy (Hoplostethus atlanticus) and smooth oreo (Pseudocyttus maculatus). Although a high proportion of features in the depth range 500-1000 m have been fished, very little is known about the ecological impacts of bottom trawling on seamounts. The potential impact is likely to be influenced by the spatial extent and frequency of fishing. A new index is presented to assess the relative intensity of trawling on New Zealand seamounts. The fishing effects index (FEI) incorporates information on the density of fishing on the seamount as a proportion of the seabed area and also on tow direction. Detailed fisheries data from more than 250 000 tows were examined to calculate FEI for New Zealand seamounts. The most intensively fished seamounts were on the south Chatham Rise, an area characterised by a large number of relatively small features which were fished serially for orange roughy in the 1980s and 1990s. Other seamounts with high FEI were on the north Chatham Rise, Challenger Plateau, and off the east coast of the North Island. A range of sensitivity analyses indicated that the general rankings of seamounts were relatively robust to the choice of arbitrary thresholds used to assign tows to seamounts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Quantifying the relative intensity of fishing on New Zealand seamounts

O’Driscoll

Clark

2005

New Zealand Journal of Marine and Freshwater Research

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“…It has been estimated that 200 to 400% of the surface area of Georges Bank is subject to disturbance by bottom trawls and dredges annually (Auster et al 1996). This can remove and/or dislodge sessile invertebrates such as sponges, bryozoans, ascidians and anthozoans that provide much of the structural complexity in these low-relief areas of the continental shelf (Collie et al 1997, Freese et al 1999, Kaiser et al 2000, Pitcher et al 2000. In the eastern Bering Sea, where both juvenile halibut and rock sole are abundant, large sessile invertebrates are significantly less abundant in trawled than in untrawled areas .…”

Section: Implications For Ecosystems and Fisheriesmentioning

confidence: 99%

Behavioral mechanisms underlying the refuge value of benthic habitat structure for two flatfishes with differing anti-predator strategies

Ryer¹,

Stoner²,

Titgen³

2004

Mar. Ecol. Prog. Ser.

109

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Juvenile flatfish habitat is usually modeled on the basis of sediment grain-size, depth and temperature. Recent evidence indicates that some juvenile flatfishes associate with emergent structures such as sponge, shell and other biogenic and bed-form features of otherwise low-relief shelf habitats. In laboratory experiments we examined the habitat preference and effects of habitat structure upon predation vulnerability of sub-yearling (Age-0) Pacific halibut Hippoglossus stenolepis and northern rock sole Lepidopsetta polyxystra. When given the choice between bare sand or sand with 16% sponge coverage, halibut demonstrated strong preference for sponge, while rock sole showed no preference. Larger Age-2 halibut (used as predators in the subsequent experiment) also preferred sponge, but this preference declined with increasing hunger. When allowed to forage for Age-0 flatfishes in either bare sand or sponge, predators consumed more prey in sand and consumed more Age-0 halibut than rock sole. We were able to determine which behavioral processes in the predator-prey interaction were modified by the presence of habitat structure. Predator-prey encounter rates decreased in the sponge habitat as predator search was impeded: predators paused more frequently and swam more slowly to maneuver through the sponges. Sponges also tended to hinder the pursuit of prey. Rock sole utilized stereotypic flatfish defense-mechanisms, relying upon immobility, burial and crypsis, and were less likely to flush at a predator's approach than halibut. Halibut have a less developed ability to mimic sediments, but a deeper/narrower body that confers greater swimming speed, and were more likely to flush as a predator approached. Once they had flushed and were pursued by a predator, halibut were more likely to escape than were rock sole. These experiments support an accumulating body of evidence that emergent structure, in otherwise low-relief benthic habitats, may play an important role in the ecology of some juvenile flatfishes. Removal of emergent structure by towed fishing gear and other anthropogenic and/or natural disturbance may influence patterns of distribution for juvenile halibut, as fish redistribute to less preferred habitat, and may decrease survival rates through increased losses to predation.

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“…Such habitats are undoubtedly a major, but poorly known, reservoir of marine biodiversity, and their structural complexity provides habitat for a variety of other species. In some regions they have been fished intensively enough to produce changes in compositions of fish (Sainsbury et al 1997, Laurans et al 2004) and megazoobenthos communities (Pitcher et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Inter-reef vertebrate communities of the Great Barrier Reef Marine Park determined by baited remote underwater video stations

Cappo¹,

De’ath²,

Speare³

2007

Mar. Ecol. Prog. Ser.

135

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A fleet of baited remote underwater video stations was set in lagoonal and inter-reef waters of the Great Barrier Reef Marine Park, across 14°of latitude and the entire shelf. Counts of the maximum number seen in any one field of view were used to estimate relative abundance of 347 species of bony fishes, cartilaginous fishes and sea snakes. Boosted regression trees were used to assess the influence of depth and location of sampling sites on species richness. Multivariate regression trees and indices of specificity and fidelity (Dufrêne-Legendre indices) were used to distinguish 17 spatially contiguous vertebrate groups within a hierarchy of spatial scales. Location across the shelf and depth had the greatest influence on species richness, with peaks occurring around the ~35 m isobath in the inter-reef waters of the reef matrix, coinciding with shallow banks and shoals. Richness increased slightly toward the equator. Nine terminal vertebrate communities parallel to the coast were distinguished inshore and offshore in deep and shallow water along a latitudinal gradient. There were important community boundaries at Bowen in the south, Townsville in the centre, and Cape Flattery in the north. Latitudinal groupings were most evident inshore. Offshore communities were spatially extensive and separated lagoonal, mid-shelf and outer-shelf sites. Community boundaries were correlated with knowledge of strong gradients in sedimentary and oceanographic processes influenced by the shape of the reef matrix and regional tides and currents.

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Implications of the effects of trawling on sessile megazoobenthos on a tropical shelf in northeastern Australia

Cited by 71 publications

References 13 publications

Quantifying the relative intensity of fishing on New Zealand seamounts

Quantifying the relative intensity of fishing on New Zealand seamounts

Behavioral mechanisms underlying the refuge value of benthic habitat structure for two flatfishes with differing anti-predator strategies

Inter-reef vertebrate communities of the Great Barrier Reef Marine Park determined by baited remote underwater video stations

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