Impact of fishing on size composition and diversity of demersal fish communities

Bianchi, G.

doi:10.1006/jmsc.2000.0727

Cited by 327 publications

(255 citation statements)

References 22 publications

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“…Although originally designed to provide fisheries independent information for fish stock assessment and management, they are now increasingly being used to analyse trends in the abundance, distribution and diversity of both commercial and non-commercial species of fish and epibenthos (e.g., Bianchi et al 2000;Shackell and Frank 2003;Daan et al 2005;Perry et al 2005;Atkinson et al 2011). …”

Section: Bottom Trawl Surveysmentioning

confidence: 99%

Methods for the Study of Marine Biodiversity

Costello

Basher

McLeod

et al. 2016

The GEO Handbook on Biodiversity Observation Networks

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Recognition of the threats to biodiversity and its importance to society has led to calls for globally coordinated sampling of trends in marine ecosystems. As a step to defining such efforts, we review current methods of collecting and managing marine biodiversity data. A fundamental component of marine biodiversity is knowing what, where, and when species are present. However, monitoring methods are invariably biased in what taxa, ecological guilds, and body sizes they collect.

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Section: Bottom Trawl Surveysmentioning

confidence: 99%

Methods for the Study of Marine Biodiversity

Costello

Basher

McLeod

et al. 2016

The GEO Handbook on Biodiversity Observation Networks

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“…Recent extensions of this idea demonstrate that size composition changes with increased F (Gislason and Rice 1998;Bianchi et al 2000), although such studies, as applied mostly to fish communities and ecosystems, illustrate general trends rather than linking size-related measures to RPs (Rochet and Trenkel 2003). Given that catch length frequencies are among the easiest data to collect, it is valuable to know how to interpret such information in the context of providing directed fishery management advice.…”

Section: Length-based Reference Points and Harvest Control Rulesmentioning

confidence: 99%

Length‐Based Reference Points for Data‐Limited Situations: Applications and Restrictions

2009

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Current fisheries management policies generally require an assessment of stock status, which is a difficult task when population and fisheries data are limited. Three simple metrics based on catch length compositions (i.e., that reflect exclusive take of mature individuals, P mat; that consist primarily of fish of optimal size, the size at which the highest yield from a cohort occurs, P opt; and that demonstrate the conservation of large, mature individuals, P mega) can be used to monitor population status relative to exploitation. The metrics (collectively referred to as Px) were intended to avoid growth and recruitment overfishing, but there was no quantitative linkage to stock status and calculation of future sustainable catches. We attempt to make this connection by exploring the relationship of Px measures to fishing mortality and spawning biomass (SB). The relationships are compared specifically to the current target reference point (0.4 times the virgin, or unfished, SB [SB0]) and limit reference point (0.25SB0) used for the U.S. West Coast groundfish fishery by using simulations based on a deterministic age‐structured population dynamics model. Sensitivity to fishery selectivity, life history traits, and recruitment compensation (steepness) is explored. Each Px measure showed a wide range of possible values depending on fishery selectivity, steepness, and the ratio of the length at maturity (L mat) to the optimal fishing length (L opt). Although the values of Px may be compatible with sustainable fishing, these values are not always sufficient to ensure stock protection from overfishing. Moreover, values for Px cannot be interpreted adequately without knowledge of the selectivity pattern. A new measure, P obj (the sum of P mat, P opt, and P mega), is introduced to distinguish selectivity patterns and construct a decision tree for development of stock status indicators. Heuristic indicator values are presented to demonstrate the utility of this approach. Although several caveats remain, this approach builds on the recommendations of previous literature by giving further guidance related to interpreting catch length composition data under variable fishery conditions without collecting additional information. It also provides a link to developing harvest control rules that inform proactive fisheries management under data‐limited conditions.

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“…Trawling modifies the ecosystem structure and species interactions, with nu-merous consequences including changes in the trophodynamics. A mix of direct and indirect effects is often observed at the food web level, the main one being a decrease in the mean trophic level as a consequence of the removal of larger individuals, which are generally predators (Bianchi et al 2000, Pauly et al 1998. Changes in the diet of fish can occur because of extra supply of organic matter from organisms killed or injured by the trawl gear and from discards that become food for opportunistic species (Kaiser and Spencer 1994).…”

Section: Introductionmentioning

confidence: 99%

Assessing the effects of a trawling ban on diet and trophic level of hake, <i>Merluccius merluccius</i>, in the southern Tyrrhenian Sea

Sinopoli¹,

Fanelli²,

D’Anna³

et al. 2011

Sci. Mar.

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SUMMARY: This study assesses the effects of a trawling ban on the diet and trophodynamics of the hake Merluccius merluccius by comparing stomach contents and stable isotopes (δ 15 N and δ 13 C) in two trawled gulfs and one untrawled gulf in northern Sicily (western Mediterranean). Comparisons were made for three size classes of hake encompassing 60 to 410 mm total length. Fish were collected from 50 to 200 m depth on muddy bottoms. The diets of hake of small and medium size were similar overall but more selective in the untrawled gulf. Greater differences were detected between the diets of larger specimens from trawled and untrawled areas. In the untrawled gulf large hake mainly preyed on clupeoid fish, while in the trawled gulfs other fish prey were found in the stomach contents. δ 15 N values of hake did not vary significantly between trawled and untrawled areas, while there was a clear effect of size, with larger individuals being significantly more enriched than juveniles. Conversely, δ 13 C values were generally more depleted for individuals collected in the untrawled area, suggesting a more pelagic source of carbon. The results from the mixing model agree fairly well with the known feeding habits found for each size class in each area.Keywords: diet, fishing impact, Merluccius merluccius, stable isotopes, trophodynamics, Mediterranean. RESUMEN: Efectos de un área de veda a la pesca de arrastre sobre la dieta y el nivel trófico de la merluza, Merluccius Merluccius, en el sur del Mar Tirreno. -Este estudio evaluó los efectos de la pesca de arrastre comercial en la dieta y la trofodinámica de la merluza mediterránea, Merluccius merluccius, mediante la comparación de sus contenidos estomacales y de la composición isotópica (δ 15 N y δ 13 C) en dos golfos donde está permitida la pesca de arrastre y en uno donde está prohibida, en el norte de Sicilia (Mediterráneo Occidental). Las comparaciones se hicieron para tres clases de talla que abarca la merluza entre 60 y 410 mm de longitud total. Los peces fueron recolectados en los fondos fangosos de la plataforma continental de 50 a 200 m de profundidad. Los hábitos alimenticios de las merluzas pequeñas y medianas eran similares, pero más selectivo en el golfo donde la pesca está prohibida. Las mayores diferencias se produjeron en la dieta de los especímenes más grandes comparando los golfos arrastrados con el golfo protegido. En el área protegida las merluzas grandes cazaban sobre todo en clupeidos y engráulidos, mientras que otros peces se encuentran en el contenido estomacal de M. merluccius de las áreas de pesca. Los valores de δ 15 N de la merluza no variaron significativamente entre las áreas protegidas y no protegidas, mientras que hubo un efecto claro de la talla: valores más alto, se han observado en los animales más grandes. Por el contrario los valores de δ 13 C fueron en general más empobrecidos (más negativos) en los ejemplares recolectados en el área protegida, esto indica una fuente más planctónica de carbono. Los resultados de los mixing models concue...

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Impact of fishing on size composition and diversity of demersal fish communities

Cited by 327 publications

References 22 publications

Methods for the Study of Marine Biodiversity

Methods for the Study of Marine Biodiversity

Length‐Based Reference Points for Data‐Limited Situations: Applications and Restrictions

Assessing the effects of a trawling ban on diet and trophic level of hake, <i>Merluccius merluccius</i>, in the southern Tyrrhenian Sea

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