Nathan G. Taylor

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• PhD
• Bycatch coordinator at International Commission for the Conservation of Atlantic Tunas

Knowledge of the spatiotemporal behavior and interactions with fishing gear of bycatch species is essential to improve conservation and fisheries management strategies. We analyze fine-scale data from onboard observers, covering 25 fishing fleets from 2002 through 2018, to assess temporal trends and spatial variation in sea turtle bycatch in longli...

Fisheries can adversely affect threatened bycatch species and vulnerable marine ecosystems (VMEs). Thresholds are unique amongst bycatch management methods in providing flexibility in individual participants' approaches to avoid exceeding limits, and particularly for individual vessel quotas , in incentivizing the innovation of effective and commer...

There is growing concern over the conservation status of sharks and relatives exposedto fishing mortality. The Food and Agriculture Organization of the United Nations in1999 adopted the International Plan of Action for the Conservation and Managementof Sharks (IPOA), which provides nations with advice on adopting and implementingnational plans. An...

An individual tagging model was implemented within the spatial, seasonal, multi-stock, multi-fleet operating models of the peer-reviewed Management Strategy Evaluation (MSE) framework for Atlantic bluefin tuna to evaluate the benefits of a harvest strategy that utilizes conventional gene tagging. A multi-year Brownie estimator was developed to test...

The pelagic fisheries beyond the continental shelves are currently managed with a range of tools largely based on regulating effort or target catch. These tools comprise both static and dynamic area‐based approaches to include gear limitations, closed areas and bycatch limits. There are increasing calls for additional area‐based interventions, part...

Basking shark Cetorhinus maximus and white shark Carcharodon carcharias are both species of low productivity. Whilst life-history data are limited for both species are limited, published estimated rates of population growth are low (r = 0.1346 year-1 for basking shark, and 0.026 to 0.074 year-1 for white shark). Both species are of conservation con...

This document presents a compact closed-loop simulation framework for blue shark management strategy evaluation (MSE). The approach relies on building operating models using Bayesian prior distributions for key life-history parameters and productivity, considering management procedure (MP) types that ICCAT has already employed, and tuning MPs to mi...

Biological information for mobulid rays is summarised for the ICCAT area. At least five valid species occur in this area, although taxonomic uncertainties means that the number of accepted species may change over time. Management regulations applying to mobulids would be applied most effectively at the family-level. Whilst life-history data are lim...

We reviewed the management measures related to management strategy evaluation We defined a set of data fields to create a database of Performance Indicators and associated probability requirements, as well as objectives for desired stock status, yield, and safety (as expressed by limit reference points, LRPs), and variability in yield. We show that...

This document summarizes the approach for swordfish close-loop simulations and progress to date. The approach uses two methods to characterize uncertainties in operating models. The first of these is to use multivariate priors to characterize uncertainty in life-history parameters and productivity. The second of these approaches is to capture the u...

A multi-species, multi-fleet operating model was developed for the North Atlantic longline fishery including two primary species (swordfish and bigeye tuna) and four secondary species (blue shark, shortfin mako shark, white marlin, blue marlin). The operating model was used to generate a wide range of future exploitation scenarios for the various s...

There is growing concern over the conservation status of sharks and relatives exposed to fishing mortality. The Food and Agriculture Organization of the United Nations in 1999 adopted the International Plan of Action for the Conservation and Management of Sharks (IPOA) which provides nations with advice on adopting and implementing national plans....

Climate change impacts on fish stocks may include changes in ecological interactions, spatial redistribution, and changes in productivity. Predicting precisely what will happen to fish stocks with any future climate changes is challenging. Climate change science could be used in the assessment process a) using indicator-based approaches to provide...

Conventional tagging data of North and South Atlantic blue shark stocks were reviewed, and preliminary analyses were performed for its use within the stock evaluation. The tag releases and recapture records were revised, updated, and standardized, to summarize size distributions, time at large and distance displacement between release and recapture...

We obtain estimates of life history parameters and steepness from the FishLife database that contains the metanalytical information from Fishbase and from Myers Legacy data. The first stage in the estimation process was to conduct the analysis using the existing records in the FishLife database. The second stage was to update the analysis with most...

This document presents a method for clustering CPUE series with similar trends and applies it for Southern CPUE series. The method consists of visual examination of the series with Lowess fitting, residual plots, cross-correlation analysis, and hierarchical cluster analysis. The hierarchical cluster analysis uses complete linkage clustering. This c...

Estimates of vital rates and population dynamics parameters of the North and South Atlantic stocks of blue shark (Prionace glauca) for potential use as inputs into production and integrated stock assessment models were computed based on biological information gathered at the 2023 Data Preparatory meeting. Six methods were used to compute determinis...

A Benchmark Workshop for selected elasmobranch stocks (WKELASMO) was convened to evaluate the appropriateness of data and methods to assess and provide short-term forecast of four stocks: Porbeagle in the Northeast Atlantic (por.27.nea), thornback ray in the Bay of Biscay (rjc.27.8), undulate ray in the Channel (rju.27.7de), and cuckoo ray in weste...

ICES has scheduled for 2021/22 an assessment evaluation for the northeast porbeagle (Lamna nasus) stock and invited the participation of ICCAT. This document presents a review and comparison of the catch data series (1926-2020) available from the ICES data call and the ICCAT fisheries statistics for this stock. A comparison with the catch series us...

We present some preliminary closed-loop simulations for South Atlantic swordfish. We condition an Operating Model using OpenMSE's Rapid Conditioning Model and using a joint multivariate prior for steepness derived from maturity, growth and natural mortality information from northern swordfish to integrate across the uncertainty in these quantities...

One potential problem with applying any Management Procedure that requires an index of abundance is that there is only one potential CPUE series, a Spanish longline series that is likely available in the future for management of the eastern Atlantic porbeagle stock. In this fishery, Porbeagle shark are a bycatch species so that there are concerns a...

There is a need for rigorous science to inform decision makers for Ecosystem Based FisheriesManagement (EBFM). It is important to establish challenging and plausible scenarios forecosystem dynamics and then test whether current and potential indicators can reflect stockstatus. Without the validation of indicators and the testing of relevant policy...

Bayesian State-Space Surplus Production Models were fitted to Northeastern Atlantic porbeagle shark (Lamna nasus) catch and relative abundance indices using the 'JABBA' R package. This document presents details on the model diagnostics and stock status estimates for preliminary scenarios. A ref model was fitted to three indices reviewed by the ICES...

We expanded the derivation of the Beverton and Holt steepness parameter h by Sharma and Arocha 2017 by simulating steepness values for a range of input parameters, including natural mortality, von Bertalanffy growth, maturity and early life history information. We derived or assumed standard deviations for the 15 quantities used for this derivation...

The SCRS plans to conduct stock assessments for North and South Atlantic swordfish in 2022. During the review of the catch and size data, it was suggested that the ICCAT Swordfish Species Group needed to review the fleet structure used in the 2017 Stock Synthesis assessment. If the ICCAT Swordfish Species Group intends using Stock Synthesis for the...

Regional Fisheries Management Organisations have the responsibility to manage not just the main commercial stocks but also by caught species that may be endangered, threatened or protected and the associated communities. Although ICCAT has over a hundred species in its database, only 15 stocks have been formally assessed. This is due either to lack...

The three main robustness tests, senescence, growth curve for eastern stock, "Brazilian" catches, had already been coded in July 2020 (with 4 Operating Models (OMs) each), but the "Brazilian" catches test needed to be redone. Robustness tests on time-varying mixing and persistent change in mixing have now also been coded (with 2 OMs each) and will...

The Group reviewed the most up-to-date swordfish (SWO) fishery statistics (T1NC: Task I nominal catches; T2CE: Task II catch & effort; T2SZ: Task II size frequencies; T2CS: Task II catch-at-size reported) and conventional tagging data, available in the ICCAT database system (ICCAT-DB). The three swordfish stocks (SWO-N: North Atlantic; SWO-S: South...

In conjunction with the proposal to develop an Ecosystem report card for ICCAT, the Subcommittee met online May 4-6, 2020 to review progress on the inter-sessional exercise to update the status of the 11 ecosystem components that were identified. The indicators described in the assessments were used to form the basis for a revised prototype report...

Here we summarize a new method to impute effort using ICCAT's Task 2 catch and effort data (T2CE). The basic methodology consists of raising reported effort using the coverage ratio (CovRatio) statistic reported by CPCs in their annual Task 2 submissions. Missing values for the CovRatio statistic are imputed hierarchically using the most detailed d...

Here we summarize a new method to impute effort using ICCAT's Task 2 catch and effort data (T2CE). The basic methodology consists of raising reported effort using the coverage ratio (CovRatio) statistic reported by CPCs in their annual Task 2 submissions. Missing values for the CovRatio statistic are imputed hierarchically using the most detailed d...

Atlantic Bluefin Tuna Stock Assessment

Intersessional work had explored many alternative weightings of the different datasets and priors, but it was not possible to find any Operating Model (OM) configurations that fitted reasonably well to all datasets and passed all acceptability standards set by the Group. The basic problems were that the available data did not permit reliable estima...

By changing the ST09 form format in 2018, the SCRS reduced its ability to answer the number of questions corresponding to ICCAT Commission recommendations using this data, from 35 that could be addressed using the 2015-2017 versions of the form to just two that could be definitively addressed, 13 that could perhaps be addressed, and 20 that could n...

Regional Fisheries Management Organisations have the responsibility to manage not just the main commercial stocks but also by caught species that may be endangered, threatened or protected and the associated communities. Although ICCAT has over a hundred species in its database, only 15 stocks have been formally assessed. This is due either to lack...

A Sustainability Assessment for Fishing Effects (SAFE) was conducted for the porbeagle shark in the North and South Atlantic oceans. The SAFE approach is a quantitative assessment that computes a proxy for fishing mortality rate as the product of four susceptibility components: availability of the species to the fleets, encounterability of the gear...

Of the bluefin tuna stocks, the assessment of Atlantic Bluefin tuna is particularly difficult because the stocks are both highly migratory and mixed over much of their geographical range. The Multistock Age Structured Tag Integrated model, MAST, was built to address this problem. While MAST solved some of the analytical needs for Atlantic Bluefin t...

This study presents an improved version of the methodology used by the Secretariat to obtain global scores on fisheries statistics (Task I and Task II data) availability. A deterministic score function was adopted to estimate quantitative scores for 26 species-stock combinations (10 major tuna & tuna like species, and 3 major sharks): the global sc...

We describe an unbiased length-based, age-structured mark-recapture (LAMR) model for estimating length-based abundance and recruitment of fish populations. Many mark-recapture studies employ capture gear that is size-selective, leading to a larger and faster growing marked sub-population with a different capture probability than the unmarked sub-po...

We describe an unbiased length-based, age-structured mark-recapture (LAMR) model for estimating length-based abundance and recruitment of fish populations. Many mark-recapture studies employ capture gear that is size-selective, leading to a larger and faster growing marked sub-population with a different capture probability than the unmarked sub-po...

We develop a multi-model approach to explore how abundance of a forage fish (Pacific sardine Sardinops sagax) impacts the ecosystem and predators in the California Current, a region where sardine and anchovy Engraulis mordax have recently declined to less than 10% of contemporary peak abundances. We developed or improved applications of three ecosy...

Atlantic bluefin tuna (Thunnus thynnus) is currently managed as separate eastern and western stocks. However, tagging and otolith chemistry patterns suggest that the two stocks mix seasonally and return to natal areas to spawn. Using a simulation model, we explored how scenarios of population-specific migration and uncertainty in aspects of bluefin...

We introduce a Lagrangian movement model that can be used to characterize cyclic migrations of iteroparous fish populations. We demonstrate how movement parameters can be estimated using conventionally available catch-at-age data and provide a description of the potential bias that may arise from model misspecification, data aggregation, and nonsta...

This document presents stock assessments for Pacific Herring (Clupea pallasii) in British Columbia waters using data current to 2013. Results of the work are intended to serve as advice over the short term to fishery managers and stakeholders on current stock status and likely impacts of different harvest options. As in previous work, an integrated...

Ecosystem models are valuable tools for informing fisheries management due to their ability to simulate the spatial dynamics of modelled species, their trophic interactions, and their responses to fishing in an ecosystem context. In this study, we developed an OSMOSE (Object- oriented Simulator of Marine Ecosystems Exploitation) model for the Pacif...

Ecosystem models are valuable tools for informing fisheries management due to their ability to simulate the spatial dynamics of modelled species, their trophic interactions, and their responses to fishing in an ecosystem context. In this study, we developed an OSMOSE (Object-oriented Simulator of Marine Ecosystems Exploitation) model for the Pacifi...

What do you do when there are just enough data to show that there are mixed stocks, spread over multiple management units but without enough data to defensibly parameterize a spatial assessment model? Here I use the spatial mixed stock assessment of Atlantic Bluefin Tuna that I built to illustrate the kind of scenario that make the tradition time-s...

Atlantic bluefin tuna (Thunnus thynnus) is currently managed as two separate eastern and western stocks, despite information indicating considerable stock mixing. Using a simulation model, we explored how scenarios of population-specific migration and uncertainty in aspects of bluefin tuna biology affect the magnitude, distribution, and mixed stock...

Harvest control rules applied to aggregates of individual stocks or life history types can have pronounced small scale effects. Pacific Herring are currently managed as discrete stocks (5 major, 2 minor), and historical analyses of mark-recapture tagging data are consistent with this approach. Spatial distribution within discrete stocks may be both...

Pacific Hake (Merluccius productus) are the most abundant groundfish off the west coast of the USA and Canada, and four large cohorts have supported nearly half of the cumulative coast-wide catch since 1981. These cohorts created wide fluctuations in abundance, yet the total catch of hake has remained mostly between 250,000 and 360,000 mt per year...

Forage shes are ecologically and economically important low trophic level species, and in recent years interest in their biology and management has intensi ed. Paci c Herring are emblemat- ic of the management issues facing forage species—they are central components of the Northeast Paci c pelagic food web and support important commercial sheries....

https://www.taylorfrancis.com/books/9781317615170

Spatial-temporal assessment methods capture alternative population dynamics of bluefin tunas but also expose new analytical and management challenges. We briefly review some current spatial assessment methods. We describe the motivation for the Multistock Age Structured Tag integrated assessment model (MAST) that was developed for Atlantic bluefin...

Pacific herring abundance is currently assessed using a statistical catch-age-model. The catch-age model is fitted to commercial catch, proportions-at-age and fishery-independent survey index to estimate biomass and recruitment and to generate 1-year forecasts of spawning biomass (Martell et al., 2012; DFO 2014, 2015). A revised catch-at-age model...

Atlantic bluefin tuna is currently managed as separate eastern and western stocks. However, tagging, genetics, contaminants, and otolith chemistry patterns indicate considerable stock mixing. We developed a simulation model to explore the consequences of bluefin tuna population structure and movement on stock productivity and composition. The analy...

ONE PAGE SUMMARY The stock assessment model for 2015 is similar in structure to the 2014 model with addition of fishery data from 2014 and minor refinements to data including catch estimates from earlier years. The stock assessment is fit to an acoustic survey index of abundance and age compositions from the survey and commercial fisheries. Ther...

Summarized the coordinated efforts of multiple field programs to collect data related to pelagic ecosystem monitoring

Atlantic bluefin tuna is currently managed as separate eastern and western stocks. However, tagging and otolith chemistry patterns indicate stock mixing. We developed a simulation model to explore the consequences of bluefin tuna population structure and movement on stock productivity and composition. The analytical framework is a stochastic, age-s...

This document provides the stock assessment and Management Strategy Evaluation results for the Pacific Hake stock in the Northeast Pacific Ocean

Review of the 2014 Hake Stock assessment

Examined the use of so-called Robin Hood approaches for doing multiple data-poor stock assessments at once

Pacific Hake (Merluccius productus) are the most abundant groundfish off the west coast of the USA and Canada, and four large cohorts have supported nearly half of the cumulative coast-wide catch since 1981. These cohorts created wide fluctuations in abundance, yet the total catch of hake has remained mostly between 250,000 and 360,000 mt per year...

Atlantic bluefin tuna are managed as separate eastern and western stocks. Tagging and otolith chemistry patterns support natal homing with mixing during non-spawning periods. We developed a simulation model for bluefin tuna to explore consequences of leading hypotheses of stock structure and mixing on stock productivity and rebuilding goals. The op...

Bioenergetics models are often used to describe the implications of changes in growth and consumption of specific wild populations, and yet most parameters are derived from a variety of laboratory studies on other populations or species, leading to questions regarding the validity of predictions. A novel bioenergetics approach was recently develope...

The Pacific Region Groundfish Science Section of Fisheries and Oceans Canada applied the Ecological Risk Assessment for the Effects of Fishing (ERAEF) framework to a portion of the groundfish bottom trawl fishery in Hecate Strait, British Columbia. ERAEF was developed as a tool for informing an Ecosystem-based Approach to Fisheries Management in Au...

Annual catches by longline (LL), purse-seine (PS), bait boat (BB), and other (Oth) gears in (A) the Gulf of Mexico, (B) the Gulf of St. Lawrence, (C) the western Atlantic, (D) the eastern Atlantic, and (E) the Mediterranean Sea. (TIF)

Partial derivatives for the derivation of B0 from MSY and Fmsy (DOC)

Archival tag observation probabilities for state-space likelihoods in the MAST model for Atlantic bluefin tuna (DOC)

Description of symbols and indices used in MAST (DOC)

Electronic tag data state-transition equations in the MAST model (DOC)

Summary of key MAST model output at the posterior mode for Atlantic bluefin tuna (A) base-case with time-invariant gear selectivity and normal reporting-rate priors; (B) estimated time-invariant gear selectivity and β(3,3) reporting-rate priors; (C) estimated time-varying gear selectivity and N(0.1,0.065) reporting-rate priors; (D) base-case with e...

Estimated tag reporting rates of the MAST model for Atlantic bluefin tuna by scenario (A) base-case with time-invariant gear selectivity and normal reporting-rate priors; (B) estimated time-invariant gear selectivity and β(3,3) reporting-rate priors; (C) estimated time-varying gear selectivity and N(0.1,0.065) reporting-rate priors; (D) base-case w...

Initialization of age-structured model assuming selectivity at age, natural mortality, age-specific fecundity, and Beverton-Holt recruitment (DOC)

State dynamics and observation model (DOC)

Life-history parameters defining φ (DOC)