Drift Net Performance for Larval Fish Sampling in Rivers

Alan Couch, Fiona Dyer, Mark Lintermans, Pat Ross-Magee

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    Abstract

    Deploying small-mesh drift nets in rivers is a well-established method for sampling drifting fish larvae and eggs. Quantitative comparisons are sometimes made on the basis of numbers of larvae captured per unit volume or time. In this study a GoPro ™ camera was mounted inside the drift net to record the change in flow over time (1 to 5 minute intervals for 3 hours). Although a small number of net nights (7 nights at 3 locations) were sampled, variance in the change in flow within and between sites was observed – even during soak times as little as 2 hours. In one case there was almost no change in flow over 180 minutes but at the most extreme, the flow dropped from 8.9 m3/min to 1.5 m3/min in just 160 minutes. Variance is probably due to the level of suspended particulates at different sites or times. If volumetric or temporal estimates are made on the basis of total flow only they could in some cases be misleading and at worst make comparisons almost meaningless. While there are dedicated data logging flow meters available they are prohibitively expensive for routine sampling. Researchers could consider the method used in this study to cost effectively assess the decay in net performance during sampling.
    Original languageEnglish
    JournalPeerJ Preprints
    Volume4:e2416v1
    DOIs
    Publication statusPublished - 2016

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    drift nets
    rivers
    fish
    sampling
    flowmeters
    fish eggs
    fish larvae
    cameras
    logging
    particulates
    researchers
    deterioration
    larvae
    methodology

    Cite this

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    abstract = "Deploying small-mesh drift nets in rivers is a well-established method for sampling drifting fish larvae and eggs. Quantitative comparisons are sometimes made on the basis of numbers of larvae captured per unit volume or time. In this study a GoPro ™ camera was mounted inside the drift net to record the change in flow over time (1 to 5 minute intervals for 3 hours). Although a small number of net nights (7 nights at 3 locations) were sampled, variance in the change in flow within and between sites was observed – even during soak times as little as 2 hours. In one case there was almost no change in flow over 180 minutes but at the most extreme, the flow dropped from 8.9 m3/min to 1.5 m3/min in just 160 minutes. Variance is probably due to the level of suspended particulates at different sites or times. If volumetric or temporal estimates are made on the basis of total flow only they could in some cases be misleading and at worst make comparisons almost meaningless. While there are dedicated data logging flow meters available they are prohibitively expensive for routine sampling. Researchers could consider the method used in this study to cost effectively assess the decay in net performance during sampling.",
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    Drift Net Performance for Larval Fish Sampling in Rivers. / Couch, Alan; Dyer, Fiona; Lintermans, Mark; Ross-Magee, Pat.

    In: PeerJ Preprints, Vol. 4:e2416v1, 2016.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Drift Net Performance for Larval Fish Sampling in Rivers

    AU - Couch, Alan

    AU - Dyer, Fiona

    AU - Lintermans, Mark

    AU - Ross-Magee, Pat

    PY - 2016

    Y1 - 2016

    N2 - Deploying small-mesh drift nets in rivers is a well-established method for sampling drifting fish larvae and eggs. Quantitative comparisons are sometimes made on the basis of numbers of larvae captured per unit volume or time. In this study a GoPro ™ camera was mounted inside the drift net to record the change in flow over time (1 to 5 minute intervals for 3 hours). Although a small number of net nights (7 nights at 3 locations) were sampled, variance in the change in flow within and between sites was observed – even during soak times as little as 2 hours. In one case there was almost no change in flow over 180 minutes but at the most extreme, the flow dropped from 8.9 m3/min to 1.5 m3/min in just 160 minutes. Variance is probably due to the level of suspended particulates at different sites or times. If volumetric or temporal estimates are made on the basis of total flow only they could in some cases be misleading and at worst make comparisons almost meaningless. While there are dedicated data logging flow meters available they are prohibitively expensive for routine sampling. Researchers could consider the method used in this study to cost effectively assess the decay in net performance during sampling.

    AB - Deploying small-mesh drift nets in rivers is a well-established method for sampling drifting fish larvae and eggs. Quantitative comparisons are sometimes made on the basis of numbers of larvae captured per unit volume or time. In this study a GoPro ™ camera was mounted inside the drift net to record the change in flow over time (1 to 5 minute intervals for 3 hours). Although a small number of net nights (7 nights at 3 locations) were sampled, variance in the change in flow within and between sites was observed – even during soak times as little as 2 hours. In one case there was almost no change in flow over 180 minutes but at the most extreme, the flow dropped from 8.9 m3/min to 1.5 m3/min in just 160 minutes. Variance is probably due to the level of suspended particulates at different sites or times. If volumetric or temporal estimates are made on the basis of total flow only they could in some cases be misleading and at worst make comparisons almost meaningless. While there are dedicated data logging flow meters available they are prohibitively expensive for routine sampling. Researchers could consider the method used in this study to cost effectively assess the decay in net performance during sampling.

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