From subsidy evaluation to effort estimation: Advancing the function of voyage data recorders for offshore trawl fishery management

Chang, Shui-Kai

doi:10.1016/j.marpol.2016.09.017

Cited by 10 publications

(22 citation statements)

References 30 publications

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“…). High‐resolution measurement of fishing effort can be derived from fishery‐independent, high‐tech data, such as VMS or VDR data (Gerritsen and Lordan ; Chang and Yuan ; Chang ), in the absence of reported fishing effort. However, many fisheries are unable to afford the installation of these systems.…”

Section: Discussionmentioning

confidence: 99%

“…), or by applying fishery‐specific algorithms to fishery‐independent information, such as vessel monitoring systems (VMSs), coastal surveillance radar systems (CSRSs), or voyage data recorders (VDRs; e.g., Lee et al. ; Chang , ). The CPUE can then be calculated.…”

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confidence: 99%

“…The second task was to standardize the CPUE calculated from landings data and FDPT estimates with consideration of target effect (i.e., the effect of different fishing tactics). There are approximately 15 different fishing gears harvesting more than 200 fish species that inhabit the highly diverse coastal ecosystems off Taiwan (Chang ). Except for some key fisheries, such as the precious coral fishery or Bluefin Tuna Thunnus thynnus fisheries that have specific license regulations, fishing vessels can legally change their targets or even their fishing methods for the seasonally abundant species without reporting to the fishery authorities.…”

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confidence: 99%

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Deriving a Statistically Reliable Abundance Index from Landings Data: An Application to the Taiwanese Coastal Dolphinfish Fishery with a Multispecies Feature

et al. 2018

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Data from coastal fisheries are often incomplete, as these fisheries are usually small in scale, rendering them exempt from logbook submission requirements. The catch of Dolphinfish Coryphaena hippurus by Taiwanese fisheries once ranked second in the world but has dramatically declined to very low levels in recent years. To address this decline, assessment of a Dolphinfish abundance index was necessary. However, due to the small scale of the fisheries, logbook data were not available to calculate CPUE. This study aimed to estimate a statistically reliable index by (1) assigning effort matrices to landings data using coastal surveillance radar data; (2) standardizing the 2001-2015 CPUEs while using four approaches (classifying fishing tactics by multivariate techniques and principal components analysis) to differentiate the fisheries' effort toward catching Dolphinfish from the effort toward other target species; and (3) evaluating performance of the standardization models by using an R 2 estimated by cross-validation and bootstrap procedures. The approach that used a delta-generalized additive model with a direct principal components procedure demonstrated the best fit. This study presents an example of deriving a statistically reliable abundance index from the data-incomplete situations common for coastal fisheries, which allows for follow-up population dynamics studies. The resulting index for Dolphinfish in the Taiwanese region showed two 7-year cycles, with a prominent decline in 2015. Reasons for the fluctuation are unknown but may be due to environmental factors, the fast-growing nature of the fish, and heavy exploitation of the stock by Taiwanese fisheries.

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Section: Discussionmentioning

confidence: 99%

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Deriving a Statistically Reliable Abundance Index from Landings Data: An Application to the Taiwanese Coastal Dolphinfish Fishery with a Multispecies Feature

et al. 2018

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“…Therefore, alternative approaches are required to address this concern for understanding resource trends. One approach is to derive high-quality effort data from high-tech information systems, such as a vessel monitoring system (VMS), coastal surveillance radar system, or voyage data recorder (VDR) system [ 5 – 10 ].…”

Section: Introductionmentioning

confidence: 99%

“…The regulations require all PBF vessels to join the catch documentation scheme (CDS) to report every PBF catch to a nearby fishery radio station, providing information on the catch date, location, and weight estimate and provide a CDS document for the port inspector to verify and measure the fish length and weight. Moreover, since 2007, all vessels intending to apply for fuel subsidies from the government have been required to install a VDR [ 10 ], and since 2010, all PBF vessels larger than 20 gross registered tonnage (GRT) have been required to install a functional VMS. However, before 2010, only landing data since 2001 with 100% coverage in weight and logbook data with only a small fraction of the trips (<5%) were available.…”

Section: Introductionmentioning

confidence: 99%

Data reconstruction can improve abundance index estimation: An example using Taiwanese longline data for Pacific bluefin tuna

Chang¹,

Liu²,

Fukuda³

et al. 2017

PLoS ONE

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Catch-per-unit-effort (CPUE) is often the main piece of information used in fisheries stock assessment; however, the catch and effort data that are traditionally compiled from commercial logbooks can be incomplete or unreliable due to many reasons. Pacific bluefin tuna (PBF) is a seasonal target species in the Taiwanese longline fishery. Since 2010, detailed catch information for each PBF has been made available through a catch documentation scheme. However, previously, only market landing data with a low coverage of logbooks were available. Therefore, several nontraditional procedures were performed to reconstruct catch and effort data from many alternative data sources not directly obtained from fishers for 2001–2015: (1) Estimating the catch number from the landing weight for 2001–2003, for which the catch number information was incomplete, based on Monte Carlo simulation; (2) deriving fishing days for 2007–2009 from voyage data recorder data, based on a newly developed algorithm; and (3) deriving fishing days for 2001–2006 from vessel trip information, based on linear relationships between fishing and at-sea days. Subsequently, generalized linear mixed models were developed with the delta-lognormal assumption for standardizing the CPUE calculated from the reconstructed data, and three-stage model evaluation was performed using (1) Akaike and Bayesian information criteria to determine the most favorable variable composition of standardization models, (2) overall R2 via cross-validation to compare fitting performance between area-separated and area-combined standardizations, and (3) system-based testing to explore the consistency of the standardized CPUEs with auxiliary data in the PBF stock assessment model. The last stage of evaluation revealed high consistency among the data, thus demonstrating improvements in data reconstruction for estimating the abundance index, and consequently the stock assessment.

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A step forward to the joint management of the South China Sea fisheries resources: Joint works on catches, management measures and conservation issues

Chang

Basir³

et al. 2020

Marine Policy

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From subsidy evaluation to effort estimation: Advancing the function of voyage data recorders for offshore trawl fishery management

Cited by 10 publications

References 30 publications

Deriving a Statistically Reliable Abundance Index from Landings Data: An Application to the Taiwanese Coastal Dolphinfish Fishery with a Multispecies Feature

Deriving a Statistically Reliable Abundance Index from Landings Data: An Application to the Taiwanese Coastal Dolphinfish Fishery with a Multispecies Feature

Data reconstruction can improve abundance index estimation: An example using Taiwanese longline data for Pacific bluefin tuna

A step forward to the joint management of the South China Sea fisheries resources: Joint works on catches, management measures and conservation issues

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