Tony Pitcher

Professor

Relevant Degree Programs

 

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2019)
Ecosystem based management for Mille Lacs Lake, Minnesota under changing environmental conditions (2015)

Single-species and multi-species modelling was employed to seek options for sustainable management of Mille Lacs Lake, the second largest lake within Minnesota, known primarily for its walleye (Sander vitreus) fisheries. Managers of the lake face challenges in adapting to changes that include changing temperature of the water body, changing community structure, growing number of piscivorous birds, and an invasion of zebra mussels leading to greater water clarity. The lake experienced a historical decline in the population of cisco (Coregonus artedi)—a cold-water stenothermic forage species. Surplus production models of cisco population suggested that temperature explained 36-40% of change in cisco abundance and that the decline in the species was due to a combination of temperature increase and high fishing pressure. To rebuild the depleted stock, I concluded that strong restriction was required on cisco fisheries especially in warmer years.For multi-species analysis, I built an ecosystem model with the Ecopath with Ecosim (EwE) modelling suite using extensive field data on organism parameters and diet. The EwE model was fitted to abundance and catch data for the period 1985 to 2006. Influence of temperature on the model predictions were simulated by adding temperature data as forcing function in the EwE model. The model was driven forward 25 years to evaluate the ecosystem-wide predictions for prevailing harvesting strategies and other possible fisheries scenarios of interest to the lake managers. The ecosystem model was used to estimate single-species and ecosystem-level reference points for thirteen fished species in the lake with and without including the effects of temperature change. The analysis helped comparison of ecosystem effects and temperature effects on the estimated reference points. The EwE model sucessfully forecast most of the changes seen in the lake after the period of fitted-data from 2007 to 2012. The model was extended for evaluation of ecosystem-wide impact of zebra mussels invasion. The model predicted that the mussels population would stabilise in the lake after attaining maximum density. But during this period several species, including the important walleye, could be negatively affected by the filtration of phytoplankton by zebra mussels.

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Evaluation of design, environmental, and sustainability attributes affecting urban fisheries restoration habitat in Vancouver, British Columbia, Canada (2015)

This thesis examines how structural complexity and environmental variability affects biodiversity and species assemblages on an engineered intertidal habitat named the Habitat Skirt, and develops a rapid assessment tool (RESTORE) to evaluate the long-term sustainability of restoration areas based on ecological, social and economic indicators to inform adaptive management. First, I tested how species diversity and assemblages on the Habitat Skirt compares with riprap; and if differences can be explained by environmental factors. Diversity at the Habitat Skirt and rip-rap were similar; however, species assemblages were not (P = 0.021). Species assemblages on the Habitat Skirt were dominated by Mytilus trossulus, while riprap had greater diversity of macroalgae. Both light intensity and water motion accounted for significant variation among species assemblages (P = 0.008; P = 0.019). Light intensity was positively correlated with macroalgal cover (P = 0.014); and both were lower at the Habitat Skirt (P = 0.001) then riprap. When constructing shoreline infrastructure with limited buffers to reduce shading, habitat managers need to determine whether potential differences in species composition meet regional coastal management objectives. Second, I examine intertidal assemblages and diversity among four microhabitats on the Habitat Skirt. Species richness was greatest within tidepools from two to four metres above chart datum (m CD) and vertical habitats at zero and one m CD. Richness decreased with increasing tidal elevation, except in tidepools where richness remained similar irrespective of tidal elevation. Species composition of many microhabitats varied with tidal height, these did not change significantly during the last two years. These results show that the relative effectiveness of microhabitats vary with tidal height. Lastly, I develop a tool, RESTORE, for assessing the sustainability of restoration areas using 25 ecological, social and economic attributes. I use RESTORE in a case study to examine differences in sustainability among marine, estuarine and freshwater ecosystems. Sustainability was significantly higher in marine than estuarine restoration areas (P = 0.029) with no significant relation of area on sustainability after controlling for ecosystem. RESTORE was successful in comparing a 25 attributes to assess the long-term sustainability of restoration areas to inform future adaptive management.

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Harbour seals, transgenic coho salmon and euphausiids : food dynamics in the Strait of Georgia, British Columbia (2013)

This thesis examines top-down control and a policy of predator culling, the possible impacts of invasive species, and the bottom-up effects of zooplankton on the fish populations in the Strait of Georgia (SoG), British Columbia. In summary, my study highlights indirect interactions and strongly suggests ecosystem-based management in the SoG.For top-down control, I examined interactions between harbour seals and fisheries using Ecopath with Ecosim modelling. Harbour seals feed on herring, hake, and many other commercial fish. Many fish populations in this region have declined in recent decades, while harbour seals increased exponentially after a ban of hunting in 1970, until they reached their carrying capacity in the 1990s. However, model results indicated that a cull of harbour seals may not increase total fisheries catch in the SoG because increased hake would eat more herring. With seals absent, the SoG ecosystem may be dominated by hake. The Ecopath model was then modified to investigate the ecological impacts of invasive species with altered physiology — growth-hormone transgenic (GH) coho. GH coho have the potential to greatly increase the yield of fish farms, but could cause ecological harm should they ever invade natural systems. My model scenarios showed that GH coho may impact the whole ecosystem largely through indirect interactions. Many functional groups were impacted depending on GH coho diet. However, functional groups were more strongly impacted when a bottom-up effect was introduced by changing ocean conditions. Sensitivity analyses showed that the predictions were robust to uncertainty in model parameters although predator-prey vulnerabilities were more sensitive than Ecopath parameters. I assessed the bottom-up effects by analyzing nocturnal zooplankton samples collected from the top 20m of the water column between 1990 and 2007. An abrupt step-like decline occurred in community composition in 1998/1999, especially in euphausiids and copepods. Local environmental factors had low coherence and changes in the SoG zooplankton communities correlated more with large-scale climate forcing than with local factors. The decline in zooplankton communities may be an important factor in the lack of recovery of predatory fish, such as coho salmon and lingcod, even with fishery closures in the 1990s.

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A fuzzy logic approach to spatial management of small-scale fisheries (2012)

Fishers are an integral part of the marine ecosystem; where and how fishers allocate their fishing effort can directly affect biological outcomes. Nonetheless, the human dimensions of fisheries are often not well understood, even though the ability to anticipate fishers’ response to spatial regulations is a key aspect of successful management. My thesis addresses this challenge by developing a marine spatial management tool that balances both human and conservation variables. I conduct an empirical investigation of small-scale fishers’ spatial use patterns with the aim of understanding how fishers’ preferences and perceptions of the marine environment affect their selection of fishing locations. I find that fishers tend to fish within preferred resource spaces that are bounded by the extent of their mental maps, and that are always considered to be safe. I integrate fishers’ preferences in a fuzzy logic expert system that I develop for zoning marine spaces in data poor conditions. This system, the protected area suitability index (PASI), assesses the suitability of a site for being protected from fishing by balancing fishers’ preference for the site with the site’s conservation value. Sites that are considered to be highly suitable for protection are those that have low fisher preference and high conservation value. The PASI estimates site suitability scores that range from 0 to 10, where 10 indicates that a site is very suitable for protection. I applied the PASI in a case study of a proposed marine protected area in Sabah, Malaysia. At least 58% and up to 75% of the time, the PASI’s assessment of site suitability matched a zoning plan for no take areas that was designed through a collaborative community process. This demonstrates that the PASI is appropriate for conducting rapid site prioritisation in data poor regions of the world, and can be used as an alternative to data, time, and financially demanding spatial planning methods.

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Assessment of the Red Sea ecosystem with emphasis on fisheries (2012)

A comprehensive assessment of the Red Sea large marine ecosystem (LME), with emphasis on fisheries, was carried out using several approaches. The assessment started with a multidisciplinary rapid appraisal of the sustainability of the fisheries using standardized attributes in ecological, economic, social, technical and ethical fields. Then a time-series assessment of the fishery was carried out using data from interviews and the reconstruction of catch from 1950 - 2006. A case study to estimate the unreported catch by quantifying qualitative information on incentives to misreport was carried out for Eritrean fisheries. Finally, a comprehensive and detailed assessment was done in an ecosystem-based framework using the modelling tool Ecopath with Ecosim (EwE), which quantifies the trophic interactions of the organisms and fisheries. It was used to predict the impact of different scenarios of fisheries on the ecosystem and explore the conflict between artisanal and industrial fisheries. Uncertainty analysis was carried out for the different assessment methods employed.The results of the assessments have varying levels of detail: relative ranking of the sustainability of fisheries in the rapid appraisal assessment, relative quantitative changes over time in the interview analysis, actual historic quantitative assessment of the catches in the catch reconstruction, and finally a quantitative assessment with potential to predict future scenarios using ecosystem modelling. The results give a holistic understanding of the Red Sea ecosystem and its fisheries. The data and resources needed increased as the details of the outputs increased. The assessments complemented each other and there are similarities in the results. They all showed declines in all fisheries, except for beach seining. Sharks, the top predator of the system, showed the worst decline in all the assessments; and the interview and catch reconstruction methods gave strikingly similar results for sharks. The ecosystem modelling did not show direct impact between artisanal and industrial fishery sectors due to the lack of trophic interactions. In addition, the thesis demonstrates that fishery researchers and practitioners can utilize different assessment tools, given the resources at their disposal, to assist the management of resources to conserve ecosystems and livelihoods.

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Effects of Harvest and Climate Change on Polar Marine Ecosystems (2012)

No abstract available.

Illegal and unreported fishing : global analysis of incentives and a case study estimating illegal and unreported catches from India (2012)

Illegal, unreported and unregulated (IUU) fishing has been identified as one of theimportant drivers affecting sustainable management of fish stocks worldwide. Although,Governments have initiated regulations and institutions to address these concerns, overthe years little progress has been achieved in controlling drivers of illegal fishing. In thepost UNCLOS era, countries adopting progressive laws like the United Nations FishStocks Agreement, FAO Compliance Agreement and FAO International Plan of Actionon IUU fishing have not backed them up with adequate monitoring and surveillanceassets, leading to low compliance. Most countries within the new legal framework lackadequate institutional and enforcement infrastructure to improve fisheries compliance.The thesis employs three approaches to identify and evaluate the drivers of illegal andunreported fishing worldwide. First, a case study approach using a questionnaire wasused to determine adequacy of monitoring control and surveillance in fisheries of 41countries. Results demonstrate that monitoring control and surveillance is poor, with bothdeveloping and developed countries having problems in this area. The second approachused 1211 illegal fishing penalty cases in 109 countries to show that low penaltiesprovide economic incentives for IUU fishing to persist in many EEZs. Finally, a detailedcase study of the Indian EEZ exemplifies the problems of developing countries byevaluating various stages where illegal and unreported catches occur in commercial andsmall-scale fisheries. The study found evidence of serious decline in mesh size in severalnet fisheries. Significant evidence of the abuse of joint venture tuna fisheries also revealsthat only 20% of the actual catch is reported; with unreported by-catch as large as theactual tuna catch. Results from each of the maritime states in India (including the remoteAndaman and Nicobar Islands) reveal that 45000 to 60000 tonnes is taken annually byillegal foreign fishing vessels, while 1.2 million tonnes of discards and 293,000 tonnesremain unreported in the small-scale and commercial trawl fisheries.

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Marine ecosystem restoration with a focus on coral reef ecosystems (2011)

The declines of fish populations in ecosystems around the globe have triggered considerable interest in marine ecosystem restoration. In addition to focusing on individual fish populations, there is increased emphasis on understanding inter-species interactions and on understanding the human relationships with the ecosystems. My thesis approaches marine restoration from (a) practical aspects of considering multispecies interactions in the ecosystem (Ecopath with Ecosim models), estimating unreported and illegal catches (influence tables) and policy that considers the concerns of multiple stakeholders (Bayesian influence diagram modeling); (b) theoretical aspects of carrying capacity and fish life history analyzed using life history parameters (Population dynamics modeling). I begin my thesis by exploring the technological, socio-economic, and political history of Raja Ampat in Eastern Indonesia (my geographical focus) to understand resource management challenges and to calculate the trends in relative misreporting of fisheries catch. The unreported fish catch exceeds the reported fish catch by a factor of 1.5. My next chapter explores the ecological benefits of establishing marine protected areas for coral reef ecosystems in Raja Ampat using Ecopath, Ecosim and Ecospace models. I estimate an ideal minimum size of no-take areas— the size of no-take area at which the biomass density of reef fish reached an asymptote—to be 16 to 25 km². Analysis of biomass density of reef fish in MPAs led to questions about ecosystem carrying capacity. To explore carrying capacity, I reconstruct ancient snapper population biomass using archaeological data obtained from fish middens using equilibrium age structure model. The results show that the ancient snapper population was about 2 to 4 times higher than the modern population biomass. To model the differing utilities of different stakeholders, in the next chapter, I develop a bayesian influence diagram model. The results indicate that restricting net fisheries and implementing 25% fisheries closure are robust scenarios favored under several combinations of the modeled variables and utility functions. The final chapter explores how the life history parameters of fish species affect the population response to restoration. It is expected that slow growing species would show a greater response to protection than fast growing species.

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In search of viable policy options for responsible use of sardine resources in the Bali Strait, Indonesia (2010)

Traditional fisheries in developing countries are often marginalized from mainstream policymaking. This is crucial as many people depend on these fisheries for their livelihood. Using a case study of a traditional, medium-scale sardine (Sardinella lemuru) fishery employing paired purse seiners (slerek) in the upwelling ecosystem of the Bali Strait, Indonesia, the overall objective of this dissertation is to search for viable policy options for responsible use of the sardine resources. This is achieved by exploring issues in multiple domains: biological, ecological, social, economic and human dimensions. A synthesis of the official catch statistics shows that administrative inefficiencies and lack of good governance have created different versions of production statistics for the fishery. Not all sardine caught and landed are entirely reported; on average fishing-day, only about 45% of the catch is landed in government landing sites. Analyses show that the slerek fishery, contributes to the practise of illegal, unreported and unregulated (IUU) fishing. From 1950 to 2001, only half to one-third of what were actually caught were reported. A socio-economic analysis indicates that financial uncertainty and poverty are the main reasons for this IUU fishing practise. Poverty index of average slerek fishing households plunged from 25.7 in 2004 to -8.6 in 2008, as the loan interest rate was set up to 38% per annum and sardine are dwindling. Single-species and ecosystem-based assessments concluded that the slerek fishery has overexploited the sardine resources. Ecosystem analyses (Ecopath with Ecosim: EwE) using 20-year simulations (2001-20) suggest that climatic variability would increase the fishery; with a caveat of increased landing volatility. Insights derived from five harvest strategies tested using stochastic El Niño effects show that only 50% fishing effort reduction from the 2001 level could provide a sustainable option in the long term. Finally, an evaluation of the sustainability status of these harvest strategies was implemented using RAPFISH with a newly-proposed evaluation field, the human dimensions of traditional fisheries. Results show that trade-offs between economic and human dimension options are crucial in our case, as forgone values from human dimension option is more than what we can derive from choosing an economic option.

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Simulation models for estimating productivity and trade-offs in the data-limited fisheries of New South Wales, Australia (2009)

Recent shifts towards ecosystem based fisheries management (EBFM) around the world have necessitated consideration of effects of fishing on a larger range of species than previously. Non-selective multispecies fisheries are particularly problematic for EBFM, as they can contribute to erosion of ecosystem structure. The trade-off between catch of productive commercial species and abundance of low-productivity species is unavoidable in most multispecies fisheries. A first step in evaluation of this trade-off is estimation of productivity of different species but this is often hampered by poor data. This thesis develops techniques for estimating productivity for data-limited species and aims to help clarify EBFM policy objectives for the fisheries of New South Wales (NSW), Australia. It begins with development of an age-structured model parameterised in terms of optimal harvest rate, UMSY. UMSY is a measure of productivity, comparable among species and easily communicated to managers. It also represents a valid threshold for prevention of overfishing. The model is used to derive UMSY for 54 Atlantic fish stocks for which recruitment parameters had previously been estimated. In most cases, UMSY was strongly limited by the age at which fish were first caught. However, for some species, UMSY was more strongly constrained by life history attributes. The model was then applied to twelve species of Australian deepwater dogshark (Order Squaliformes), known to have been severely depleted by fishing. Results showed that the range of possible values of UMSY for these species is very low indeed. These findings enabled a preliminary stock assessment for three dogsharks (Centrophorus spp.) currently being considered for threatened species listing. Preliminary results suggest they have been overfished and that overfishing continues. Finally, an Ecopath with Ecosim ecosystem model, representing the 1976 NSW continental slope, is used to illustrate trade-offs in implementation of fishing policies under alternative policy objectives. Results are compared with those of a biogeochemical ecosystem model (Atlantis) of the same system, built by scientists from CSIRO. While there were large differences in model predictions for individual species, they gave similar results when ranking alternative fishing policies, suggesting that ecosystem models may be useful for exploring broad-scale strategic management options.

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Master's Student Supervision (2010 - 2018)
Identifying stakeholders' values and preferences for management of Pacific herring (Clupea pallasii) fisheries in British Columbia, Canada (2017)

It is said that fisheries management is concerned with managing people, rather than fish. Often managers must make difficult decisions under conditions of uncertain scientific predictions, conflicting demands from stakeholder groups, or high risk of harm to the resource and/or its users. Previous publications have applied decision theory and management theory to fisheries management, but such approaches may not acknowledge the legitimacy of all competing viewpoints and values. Post-normal science, on the other hand, does so explicitly, and aims to resolve conflicts through collaborative effort based on high-quality information. This thesis explores the issues surrounding political conflicts over Pacific herring (Clupea pallasii) fisheries management in British Columbia, Canada in the 2010s, with a focus on the herring stocks in Haida Gwaii waters. These fisheries offer a unique yet generalizable case of stakeholder conflict, and an opportunity to examine that conflict’s root causes through my own original framework that parses normative from descriptive claims made by competing groups, to ascertain what those groups consider quality information and desired outcomes. I present here research conducted by an interdisciplinary team between 2015 and 2017 as part of a larger project, which employed a novel value- and ecosystem-based management approach methodology developed by Lam et al. to investigate the normative values, descriptive beliefs and fishery management preferences of 47 individuals in Haida Gwaii and 28 British Columbian herring fishery participants. The semi-structured interviews within the values-based component consisted of values-ranking and management scenario-preference exercises, an exercise associating respondents’ values with management scenarios, and open-ended questions on respondents’ experience and beliefs about herring and its fisheries. Analysis tabulated respondents’ value priorities and scenario preferences, and investigated descriptive beliefs about herring stocks. Results provide evidence that stakeholder groups’ nominal values are quite similar, while their preferences for management of herring stocks in Haida Gwaii are starkly different, and potentially influenced by level of trust in the opposing group and in management. This suggests that trust-building between opposing stakeholder groups, and between management and stakeholders, is a necessary first step toward conflict resolution.

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