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Jean Guillard - One of the best experts on this subject based on the ideXlab platform.

  • comparing two Fish Sampling standards over time largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    Summary We sampled Lake Bourget (surface area = 44 km2) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km2) were treated as sample units. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero Fish. Pelagic gillnetting indicated that small ( 20 m) increased significantly after 2005. Both surveys showed whiteFish biomass increased significantly during the study, but whiteFish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small Fish and a low catch of large Fish in different years can provide similar average BPUE estimates. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears Sampling different components of the Fish community. Conversely, in pelagic habitat, where the Fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

  • Comparing two Fish Sampling standards over time: largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    1. We sampled Lake Bourget (surface area=44km(2)) using CEN standard gillnet and provisional standard acoustic survey methods over 3years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich etal., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25-5.45km(2)) were treated as sample units. 3. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50m caught zero Fish. 4. Pelagic gillnetting indicated that small (

  • Fish population surveys in estuaries: a comparison between acoustic at moored stations and purse seine surveys
    2006
    Co-Authors: Luis Tito De Morais, Jean Guillard, Monique Simier, Ibrahima Sow, Jean Raffray, Jeanjacques Albaret
    Abstract:

    In most estuarine ecosystems, the Fish biomass is difficult to estimate, since most of the standard Sampling methods are difficult to implement and may be limited to certain biotopes. Moreover, Protected Areas are no longer limited to marine ecosystems and several protected areas have been created in estuaries, lagoons or mangrove environments. In these areas, turbid waters do not allow direct diving observations and Fish Sampling, often performed using destructive – because efficient and non selective - gears such as trawling or seine nets, is always an ethic problem. As a consequence there is an increased need for liable, non-destructive methods to study Fish assemblages in these environments. In order to describe the Fish biomass distribution and evolution in the Gambia estuary, five research surveys have been conducted at different hydrological seasons. The Fish assemblages were sampled by vertical echo-sounding at moored stations and at the same time and same location with a purse seine. The purpose of this work, still in process, is to compare the two methods, to try to inter-calibrate them and to seek for their complementarity. Though significant, the global direct correlation between estimations of biomass performed with the two Sampling methods were too low to be considered satisfactory. Moreover the level of correlation between the two methods varies extensively following the survey, the season or the zone of the estuary taken into account. The role of the main environmental variables: depth, salinity, transparency and current strength on the quality of the correlation of the estimation made by the two methods was emphasized.

Daniel L. Yule - One of the best experts on this subject based on the ideXlab platform.

  • comparing two Fish Sampling standards over time largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    Summary We sampled Lake Bourget (surface area = 44 km2) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km2) were treated as sample units. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero Fish. Pelagic gillnetting indicated that small ( 20 m) increased significantly after 2005. Both surveys showed whiteFish biomass increased significantly during the study, but whiteFish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small Fish and a low catch of large Fish in different years can provide similar average BPUE estimates. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears Sampling different components of the Fish community. Conversely, in pelagic habitat, where the Fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

  • Comparing two Fish Sampling standards over time: largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    1. We sampled Lake Bourget (surface area=44km(2)) using CEN standard gillnet and provisional standard acoustic survey methods over 3years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich etal., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25-5.45km(2)) were treated as sample units. 3. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50m caught zero Fish. 4. Pelagic gillnetting indicated that small (

Sébastien Cachera - One of the best experts on this subject based on the ideXlab platform.

  • comparing two Fish Sampling standards over time largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    Summary We sampled Lake Bourget (surface area = 44 km2) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km2) were treated as sample units. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero Fish. Pelagic gillnetting indicated that small ( 20 m) increased significantly after 2005. Both surveys showed whiteFish biomass increased significantly during the study, but whiteFish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small Fish and a low catch of large Fish in different years can provide similar average BPUE estimates. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears Sampling different components of the Fish community. Conversely, in pelagic habitat, where the Fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

  • Comparing two Fish Sampling standards over time: largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    1. We sampled Lake Bourget (surface area=44km(2)) using CEN standard gillnet and provisional standard acoustic survey methods over 3years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich etal., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25-5.45km(2)) were treated as sample units. 3. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50m caught zero Fish. 4. Pelagic gillnetting indicated that small (

Lori M. Evrard - One of the best experts on this subject based on the ideXlab platform.

  • comparing two Fish Sampling standards over time largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    Summary We sampled Lake Bourget (surface area = 44 km2) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km2) were treated as sample units. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero Fish. Pelagic gillnetting indicated that small ( 20 m) increased significantly after 2005. Both surveys showed whiteFish biomass increased significantly during the study, but whiteFish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small Fish and a low catch of large Fish in different years can provide similar average BPUE estimates. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears Sampling different components of the Fish community. Conversely, in pelagic habitat, where the Fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

  • Comparing two Fish Sampling standards over time: largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    1. We sampled Lake Bourget (surface area=44km(2)) using CEN standard gillnet and provisional standard acoustic survey methods over 3years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich etal., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25-5.45km(2)) were treated as sample units. 3. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50m caught zero Fish. 4. Pelagic gillnetting indicated that small (

Michel Colon - One of the best experts on this subject based on the ideXlab platform.

  • comparing two Fish Sampling standards over time largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    Summary We sampled Lake Bourget (surface area = 44 km2) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km2) were treated as sample units. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero Fish. Pelagic gillnetting indicated that small ( 20 m) increased significantly after 2005. Both surveys showed whiteFish biomass increased significantly during the study, but whiteFish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small Fish and a low catch of large Fish in different years can provide similar average BPUE estimates. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears Sampling different components of the Fish community. Conversely, in pelagic habitat, where the Fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

  • Comparing two Fish Sampling standards over time: largely congruent results but with caveats
    Freshwater Biology, 2013
    Co-Authors: Daniel L. Yule, Lori M. Evrard, Sébastien Cachera, Michel Colon, Jean Guillard
    Abstract:

    1. We sampled Lake Bourget (surface area=44km(2)) using CEN standard gillnet and provisional standard acoustic survey methods over 3years (2005, 2010 and 2011) as the Fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich etal., Freshwater Biology, 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25-5.45km(2)) were treated as sample units. 3. The BPUE of whiteFish (Coregonus lavaretus), perch (Perca fluviatilis) and roach (Rutilus rutilus) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50m caught zero Fish. 4. Pelagic gillnetting indicated that small (