William Harford

William Harford
Nature Analytics

PhD

About

51
Publications
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426
Citations

Publications

Publications (51)
Article
Full-text available
Data-limited fisheries frequently lack age-structure data and instead rely on length-based management and assessment methods. However, the performance of such length-based methods and control rules are often poorly understood when confronted with varying life-history characteristics. In this study, we used Length-Based Spawning Potential Ratio (LBS...
Article
Data-limited fisheries present significant challenges to fisheries management around the world. Landings data represent the simplest and most common source of fishery information, but length data of harvested species can offer particularly useful insight into the strength of fishing pressure and the status of stocks. However, unbiased length data c...
Article
Full-text available
Beverton & Holt's (1957) functional definition of maturity in fish (L50), as being the size class in which 50% of individuals begin producing gametes in some proportion to body weight, is widely used in assessment models to estimate spawning stock biomass, and manage the minimum size of capture. Standardized histological techniques for estimating L...
Technical Report
Full-text available
The bycatch estimation tool developed by Babcock (2022) was subjected to simulation testing using the species distribution model and longline simulator (LLSIM) developed by Goodyear (2021). To evaluate the efficacy of the bycatch estimation tool, generalized representations of ICCAT CPC longline fisheries were created using LLSIM and were coupled w...
Article
Extensions of single-species stock assessments to include ecosystem considerations are one step towards achieving an ecosystem approach to fisheries management. While red tide mortality has been estimated within base assessment models for both gag grouper and red grouper in the Gulf of Mexico since the late 2000 s, considerable uncertainty remains...
Article
Full-text available
As the world population grows, fisheries practitioners will be under increased pressure to address global challenges in data-limited fisheries management. With a focus on addressing localized and case-specific management needs, we provide a practical guide to the design and development of multi-indicator frameworks for fishery management. In a data...
Article
The ecosystem‐based fisheries management (EBFM) framework has a solid theoretical justification and has been embraced in principle by many regions; yet, systematic implementation remains a challenge. In regions with strong governance, single‐species stock assessment and management has been successful in ending overfishing and maintaining stocks nea...
Article
Full-text available
Recent global improvements to fisheries sustainability have been made through the adoption of more holistic management frameworks, such as the ecosystem approach to fisheries management (EAFM) and ecosystem-based fisheries management (EBFM), and a concurrent transition from a focus on single species or stocks to multispecies and ecosystems. In the...
Article
Full-text available
A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush, are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT...
Article
Full-text available
Among abalone species that were once harvested along the California coastline, red abalone (Haliotis rufescens) supports the remaining recreational fishery. To support development of a red abalone fishery management plan, non‐governmental organizations have initiated expanded data collection and developed fishery management strategies. The latter i...
Article
Maintaining fish stocks at optimal levels is a goal of fisheries management worldwide; yet, this goal remains somewhat elusive, even in countries with well‐established fishery data collection, assessment and management systems. Achieving this goal often requires knowledge of stock productivity, which can be challenging to obtain due to both data li...
Article
Full-text available
Specifying annual catch limits for artisanal fisheries, low economic value stocks, or bycatch species is problematic due to data limitations. Many empirical management procedures (MPs) have been developed that provide catch advice based on achieving a stable catch or a historical target (i.e., instead of maximum sustainable yield). However, a thoro...
Technical Report
Full-text available
Updating indices of red tide severity for incorporation into stock assessments for the shallow-water grouper complex in the Gulf of Mexico. SEDAR61-WP-07. SEDAR, North Charleston, SC. 12 pp.
Article
Harmful algal Karenia brevis blooms, known as “red tide”, are responsible for major episodic fish kills in the Gulf of Mexico. In response to management concerns, we conducted management strategy evaluation (MSE) to examine whether decision‐making reactivity to event occurrence or precautionary catch limit reductions could aid in achieving fishery...
Article
Full-text available
Data‐limited approaches to managing fisheries are widespread in regions where insufficient data prevent traditional stock assessments from determining stock status with sufficient certainty to be useful for management. Where severe data limitations persist, a catch‐only approach is commonly employed, such as in the U.S. Caribbean region. This appro...
Article
Full-text available
Depth is usually considered the main driver of Lake Trout intraspecific diversity across lakes in North America. Given that Great Bear Lake is one of the largest and deepest freshwater systems in North America, we predicted that Lake Trout intraspecific diversity to be organized along a depth axis within this system. Thus, we investigated whether a...
Data
Growth parameter estimates for three Lake Trout morphs captured in Great Bear Lake. (SE = standard error; LL = lower 95% confidence limit; UL = upper 95% confidence limit). (DOCX)
Data
Growth parameter estimates for four lake trout composite groups captured in Great Bear Lake. (SE = standard error; LL = lower 95% confidence limit; UL = upper 95% confidence limit). (DOCX)
Data
The four shallow-water morphotypes of Lake Trout from Great Bear Lake. (DOCX)
Data
Hierarchical clusters of Lake Trout individuals sampled in Dease Arm (0–150 m) overlaid on the first two principal component axes (PCA) using FactoMineR [46], in A) based on morphological grouping and in B) based on composite grouping. Grouping by the morphological procedure: Morph 1 = red circle, Morph 2 = green circle, and Morph 3 = black circle,...
Data
CVA of Lake Trout linear measurements, body shape, and head shape. Groups were identified by FactoMineR [46] based on morphological and composite group assignment. Each group is also outlined by a 68.3% confidence ellipse. For the depth procedure, groups are represented as follows: open circle = 0–20 m, light grey square = 21–50 m, and black diamon...
Data
Mean log-likelihood values (LnP[K]) for different hypothesized numbers of genetic populations (K) of Lake Trout in Great Bear Lake. Also shown is the mean value of ΔK, the ad hoc statistic of Evanno et al. [63] used to summarize the second-order rate of change in LnP(K). The bold values represent the most likely number of genetic groups for each st...
Data
Length-age models within three depth strata strata (Depth) in Great Bear Lake. Length-age models for Lake Trout captured within three depth strata (Depth) in Great Bear Lake. Each model is specified to compare growth among Lake Trout at different depths of capture (Depth), and varying growth parameters (t0, L∞,K), along with the number of parameter...
Data
Catch-per-unit-effort of adult Lake Trout captured among depth strata in Great Bear Lake. Catch-per-unit-effort (median and quartiles) of adult Lake Trout captured among depth strata in Great Bear Lake. No CPUE differences were found among the three depth strata for catch of adult Lake Trout (F2,23 = 0.12, p = 0.89). (DOCX)
Data
Systematic design of each grouping procedure used in this study, based on depth strata, morphology, and composite variables. Each grouping method used a different suite of variables to assign individuals to a group. After groups were identified, subsequent analyses followed for patterns in morphology, genetics, isotopes, and life-history parameters...
Data
Growth parameter estimates within three depth strata in Great Bear Lake. Growth parameter estimates for Lake Trout captured within three depth strata in Great Bear Lake (SE = standard error; LL = lower 95% confidence limit; UL = upper 95% confidence limit). (DOCX)
Data
Length-age models for three Lake Trout morphs captured in Great Bear Lake, Northwest Territories. Length-age models for three Lake Trout morphs (Morph) captured in Great Bear Lake, Northwest Territories. Each model is specified to compare growth among Lake Trout morphs (Morph) and varying growth parameters (t0, L∞,K), along with the number of param...
Data
Length-age models for four Lake Trout composite groups captured in Great Bear Lake. Each model is specified to compare growth among Lake Trout composite groups and varying growth parameters (t0, L∞,K), along with the number of parameters (df), log-likelihood (logLik), Akaike Information Criterion (AIC), Akaike difference (Δi), and Akaike weight (wi...
Article
Environment–recruitment relationships can be difficult to delineate with parametric statistical models and can be prone to misidentification. We use non-parametric time-series modeling which makes no assumptions about functional relationships between variables, to reveal environmental influences on early life stages of bluefin tuna and demonstrate...
Technical Report
Full-text available
Executive Summary The Gulf and Caribbean Fisheries Institute (GCFI) executed a three-year joint initiative, in partnership with the National Marine Fisheries Service (NMFS) that included a series of special sessions and workshops to address the best practices and methods to improve data-limited stock assessments of living marine resources in the G...
Article
Full-text available
A generalist strategy, as an adaptation to environmental heterogeneity, is common in Arctic freshwater systems, often accompanied, however, by intraspecific divergence that promotes specialization in niche use. To better understand how resources may be partitioned in a northern system that supports intraspecific diversity of Lake Trout, trophic nic...
Article
In data-limited fisheries, making informed management decisions based on scientific advice is challenging. Here, we evaluate a multi-indicator adaptive management framework (AMF) that allows dynamic responses to changing environmental, socioeconomic, and fishing conditions. Using stakeholder-defined goals as a foundation for specifying performance...
Article
Full-text available
In the Florida Keys coral reef ecosystem, delineation of reef fish distributions in relationship to habitat patterns is important for improving the design characteristics of fishery-independent surveys. Efficient survey design depends on analysis of fish distribution patterns to inform and improve the precision of future surveys. We used a diver vi...
Article
Limitations in data quantity and quality are common in fisheries management and affect whether and how stock assessments are carried out. We demonstrate the applicability of spatially-explicit management strategy evaluation (MSE) for connecting sampling designs of substrate-associated fishes in highly heterogeneous habitats to evaluation of stock s...
Technical Report
Full-text available
Executive Summary A special theme session and workshop on data-limited stock assessments was held at the 67th annual conference of the Gulf and Caribbean Fisheries Institute (GCFI) in Barbados, West Indies during November 3-7, 2014. Contributors to the GCFI special session provided presentations on a variety of topics relating to fishery-dependent...
Article
Full-text available
In the Florida Keys coral reef ecosystem, delineation of reef fish distributions in relationship to habitat patterns is important for improving design characteristics of fishery-independent surveys. Efficient survey design depends on analysis of fish distribution patterns as a means to inform and improve precision of future surveys. We used a diver...
Article
Full-text available
In Belize, beginning in 2011 at Glover's Reef Marine Reserve, and in 2012 at Port Honduras Marine Reserve, fishers have been required to keep logbooks to document their catch and effort. A Bayesian depletion model including in-season recruitment was applied to the standardized catch per unit effort (cpue) of Caribbean spiny lobster (Panulirus argus...
Article
While juvenile Atlantic goliath grouper, Epinephelus itajara (Lichtenstein, 1822), are known to depend on mangrove root structure, relationships with water properties (e.g., salinity) and depth remain unclear or understudied. Because availability of suitable mangrove habitat has been suggested as the primary bottleneck to the recovery of this threa...
Article
Marine reserves are becoming widely implemented along with conventional fisheries controls as integrated approaches to fisheries management. The restricted spatial distribution of fishing effort, relative to the spatial distribution of fish stocks that may be partially protected by marine reserves, often necessitates spatial considerations in the d...
Article
An ecosystem model of the western North Atlantic Ocean was constructed that emphasized predator-prey dynamics of shortfin mako, Isurus oxyrinchus Rafinesque, 1810, and bluefish, Pomatomus saltatrix (Linnaeus, 1766). Modeling served to synthesize knowledge about food consumption rates and feeding habits into a framework that could be used to charact...
Article
Full-text available
Information about bloater (Coregonus hoyi) habitat in Lake Huron was limited to correlations between commercial yield and fishing depth, despite available information from other Great Lakes. We identified seasonal patterns of bloater habitat use in hypolimnetic waters surrounding the Bruce Peninsula, Lake Huron. We applied a delta-lognormal model t...
Article
Genetic analysis of spawning lake whitefish (Coregonus clupeaformis) from six sites in the main basin of Lake Huron was conducted to determine population structure. Samples from fisheryindependent assessment surveys in the northwest main basin were analyzed to determine the relative contributions of lake whitefish genetic populations. Genetic popul...
Conference Paper
Marine protected areas (MPAs) are increasingly suggested as a means to achieve both fisheries and conservation objectives. However, a poorly understood component of MPA design theory is the manner in which movement behaviors mediate the exchange of juvenile and adult fish between no-take and fished areas. Simulation-based studies of reserve design...
Article
Small dams represent one of the most widespread human influences on riverscapes. Greater understanding of how these structures affect aquatic organisms is needed to ensure that decisions regarding their construction and removal strike an appropriate balance between components of human and ecosystem services. Within the basin of the Laurentian Great...

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