Habitat Standardization of CPUE Indices: Research Needs

Habitat standardization for billfish CPUE offers a potentially useful alternative to the statistical procedures used in the past. However, most of the assumptions of the current habitatstandardization methodology remain untested and some are not consistent with current knowledge about the behavior of billfish. This paper outlines research required to ensure the methods for habitat standardization produce robust estimates of CPUE

Habitat and Fish Population Dynamics: Advancing Stock Assessments of Highly Migratory Species

Fisheries sustainability is inherently linked to an understanding of the population-level effects of fishing. With an accurate characterization of historical fish and fishery dynamics, management agencies are more equipped to create regulations that sustain fishery resources over the long term. The overarching goal of this dissertation is to contribute to the advancement of fisheries stock assessment and promote resource sustainability. My research focused on highly migratory species (HMS), particularly fishes that reside in the open ocean. These species constitute some of the highest valued global fisheries; however, numerous factors compromise HMS stock assessment and management. These challenges are fully described in Chapter 1, which also includes corresponding research and management recommendations. A key limitation in HMS assessments underlying my research is the lack of independent scientific monitoring programs. In the absence of research surveys, HMS stock assessments must rely on fishery catch and effort data. Therefore, special care is required to infer population dynamics from entities that were not established to monitor populations. In particular, the habitat in which fishing occurs largely dictates the amount and composition of fishes captured. Unfortunately, habitat effects on fishery-dependent data are not commonly accounted for in HMS assessments. Chapter 2 presents the results of a performance evaluation of methods used for estimating HMS abundance trends, including traditional generalized linear models (GLMs), an existing method that considers habitat (statHBS), and a proposed method that hybridizes traditional and habitat-based approaches (HabGLM). I demonstrate that HabGLM was most accurate of those evaluated, while exhibiting minimal sensitivity to errors in input data. I recommend the use of HabGLM in future HMS stock assessments; however, despite being most accurate, there were scenarios where HabGLM still did not sufficiently capture the true abundance pattern. In Chapter 3, the HabGLM was applied to 35 HMS in the Atlantic Ocean using fisher logbook data from the US pelagic longline fishery. This comprehensive analysis portrays an HMS community in the Atlantic as generally depleted, with current abundances of 76% of the species at less than half of their 25-year observed maxima. However, despite these depletions, 26% of the species exhibited population growth, suggesting recent fishing intensities may be adequate for sustaining or rebuilding certain populations. While interpretations of abundance trends can be informative, fisheries management is more often guided by the output of stock assessments. Thus, in Chapter 4, I present the results of a study that evaluated the effects of abundance index quality on the performance of a stock assessment model (Stock Synthesis), with a focus on Atlantic blue marlin (Makaira nigricans). In general, assessment model performance was superior when based on abundance indices estimated using HabGLM; however, the management quantities derived from this best case scenario were still overly optimistic, and when the fisheries were regulated accordingly, population biomass was projected to be well below the management target level. Overall, my research emphasizes that (1) habitat should be directly incorporated into HMS stock assessments, and (2) independent stock monitoring programs are essential for effective fisheries management

Characterizing the Preferences and Values of US Recreational Atlantic Bluefin Tuna Anglers

The Atlantic Bluefin Tuna Thunnus thynnus is the target of a recreational fishery along the U.S. East Coast that is thought to be of considerable economic value. In some years, recreational landings have exceeded the sector’s annual subquota due to changes in fish availability, limited predictability of angler effort, and difficulties in realtime monitoring of catch. Understanding the drivers of angler behavior is critical for predicting how effort and harvest may vary as a function of changing fish availability, regulations, or costs. To investigate angler decision making, preferences, and values, we surveyed private recreational anglers from Maine to North Carolina and employed discrete choice experiments to determine how regulatory and nonregulatory trip-specific variables influence trip-taking behavior. A latent class-ranked log it model identified two distinct classes of anglers who exhibited differing preferences in regard to the importance of nonconsumptive aspects of Bluefin Tuna fishing (e.g., catch and release). Income and recent Bluefin Tuna targeting were the primary determinants of class membership, and higher-income anglers who had targeted Bluefin Tuna in the past 5 years were significantly more likely to be in the class that derives substantive benefits from nonconsumptive angling activities. An annual consumer surplus exceeding US$14 million was estimated for the 2015 fishery. We considered potential angler welfare impacts of possible management changes (compensating surplus) and identified a large amount of latent effort currently present in the fishery in the form of consumptive-oriented anglers. As a result, liberalization of harvest regulations could potentially lead to a large influx of effort into the fishery, which could impede the ability of managers to maintain harvest levels within prescribed limits

Characterizing the Biological Impacts and Human Dimensions of the U.S. East Coast Recreational Atlantic Bluefin Tuna Fishery

Atlantic bluefin tuna (Thunnus thynnus) are targeted by recreational anglers along the east coast of the United States, and the fishery is thought to be of considerable economic value. However, limited knowledge of the preferences and values of fishery participants impedes the ability of managers to maximize fishery benefits and predict harvest patterns, while an incomplete understanding of post-release mortality hinders efforts to estimate total mortality resulting from the fishery. This dissertation used a multidisciplinary approach that relied heavily on cooperative research with the recreational fishing community to examine these questions. A stated choice survey of private anglers permitted to target bluefin tuna (Chapter II) estimated a fishery consumer surplus of over $14 million in 2015 while revealing striking heterogeneity in angler preferences. Respondents placed a high value on harvesting bluefin tuna, but about half of anglers also valued non-consumptive aspects of bluefin tuna fishing such as catch-and-release. Preference segmentation was largely driven by income and recent bluefin tuna targeting behavior, with high-income anglers who had recently targeted bluefin tuna more likely to belong to the non-consumptive group. These results indicate that liberalization of harvest regulations could result in significant, non-linear increases in effort and harvest should consumptive-oriented anglers decide to re-enter the fishery. A second survey, of Atlantic bluefin tuna fishermen who possess a permit enabling them to fish either commercially or recreationally on a trip-by-trip basis, applied an online contingent sequential stated choice approach to better understand the decision-making of this unique group (Chapter III). Responses indicated that, while some permit holders consistently fish either recreationally or commercially, a substantial proportion of participants change trip type depending on fishery conditions such as prevailing fish size or regulations. The changing behavior of this latter group could potentially result in large shifts in targeting and lead to overages for the commercial handgear sector or recreational sector, and potentially the U.S. bluefin tuna quota as a whole. Lastly, post-release mortality was estimated for juvenile bluefin tuna caught in the increasingly popular light-tackle recreational fishery while also beta testing a newly developed, solar-powered pop-up satellite archival tag designed to enable large-scale, high-precision mortality studies (Chapter IV). Data were only obtained for 15 of 22 deployed tags, with 14 fish demonstrating behavior consistent with survival. One fish was predated upon, likely by a shortfin mako shark, after 17 days, and this was considered a natural rather than a fishing mortality. The low level of estimated post-release mortality, consistent with results from previous studies on different size classes of bluefin tuna caught with various angling gear types, suggests that catch-and-release angling, which Chapter II showed to be highly valued by some anglers, is a viable conservation strategy. Overall, this dissertation provides information regarding both angler preferences and fishery impacts that are of direct relevance to management. Future efforts should be directed to further engaging the recreational bluefin tuna fishing community in order to improve buy-in to management strategies and improve the ability of the United States to maintain fishing mortality within internationally prescribed limits

Evaluation of Population Structure and the Interspecific Relationship of Striped Marlin (Kajikia Audax) and White Marlin (K. Albida) Based on Traditional or Genome-Wide Molecular Markers

The istiophorid billfishes (marlins, spearfishes, and sailfish) are highly migratory pelagic fishes exhibiting broad and continuous spatial distributions in the Atlantic, Pacific, and Indian oceans. These species are targeted by a number of recreational, commercial, artisanal, and subsistence fisheries worldwide, and are also caught as bycatch in pelagic longline fisheries targeting tunas and swordfish. Though stock assessments have not been conducted for all istiophorids, assessments available for some species indicate that many istiophorid stocks are overfished and/or experiencing overfishing. However, the development of stock-specific recovery efforts is often impeded by a lack of information on basic species biology, including stock structure. The species status of some istiophorids is also uncertain, further complicating management efforts as well as strategies to conserve genetic diversity characteristic of distinct evolutionary lineages. In this dissertation, a molecular approach is used to address questions currently contributing uncertainty to the conservation and management of two istiophorid billfishes, white marlin (Kajikia albida) and striped marlin (K. audax). These closely related sister species are distributed in the Atlantic and Indo-Pacific oceans, respectively. Previous assessment of genetic population structure for white marlin based on mitochondrial (mt) DNA and five nuclear microsatellite markers suggested the possibility of population structuring for this species; however, results from the evaluation of mtDNA and 24 microsatellites across a larger number of samples, including a collection of larvae, are consistent with the presence of a single genetic stock (Chapter II). This result highlights the importance of analyses based on large numbers of molecular markers and samples, as well as a biologically informed sampling design, for studies of population structure in highly migratory pelagic species. Compared to the apparent lack of genetic population structure for white marlin, analysis of nearly 4,000 single nucleotide polymorphism (SNP) molecular markers across collections of striped marlin from the Pacific and, for the first time, Indian oceans resolved multiple genetically distinct populations (Chapter III). These populations correspond with striped marlin sampled from the western Indian Ocean, Oceania, North Pacific Ocean, and eastern central Pacific Ocean. Results from individual-based cluster analyses also suggest the presence of a second genetically distinct population in the North Pacific Ocean. Comparisons of replicate sample collections for some regions demonstrate the stability of allele frequencies across multiple generations. Finally, the uncertain species status of striped marlin and white marlin was evaluated using over 12,000 genome-wide SNPs surveyed across large numbers of exemplars per species (white marlin: n = 75, striped marlin: n = 250; Chapter IV). Results from individual-based cluster and maximum likelihood phylogenetic analyses suggest the presence of distinct evolutionary lineages for striped marlin and white marlin. This result is consistent with levels of genetic differentiation between striped marlin and white marlin which are an order of magnitude higher than those calculated between populations of striped marlin. Collectively, results of this dissertation provide practical insights for improving the conservation and management of white marlin and striped marlin, including revised stock structures which should be recognized in assessment and management plans for striped marlin. Future genomic studies should focus on addressing uncertainties regarding rangewide stock structure and species relationships for other istiophorids. Additionally, studies which continue to improve the genomic resources available for istiophorid billfishes and other large pelagic fishes may ultimately facilitate the evaluation of questions previously unexplored for the pelagic marine environment, such as localized adaptation and speciation

Fall 2012

https://nsuworks.nova.edu/occ_currents/1001/thumbnail.jp

Reconciling the Challenge of Aphanic Species Within Marine Conservation

Aphanic species are those within a taxonomic complex that may not be readily distinguishable from other sympatric species. The existence of these species is becoming apparent at an increasing rate through the use of technological tools like molecular genetic analyses. A lack of clarity on the definitions of terms used to describe similar species, how these species are identified, and how prevalent they are can confound identification, description, and management of these organisms. This review collects and defines the terms used to describe these hidden species and suggests the use of the term aphanic for situations where additional information (and therefore classification) is not yet known. The review also addresses species identification methods and upholds the recommendation that newly proposed aphanic species should be validated by the use of two or more methods, such as morphological assessments alongside DNA identifications. Additionally, five historical case-study examples lead to the recommendation that management of newly-discovered aphanic species should remain managed under the species it is found within until information relating to each species’ risk is understood. Information must then be pushed to and evaluated by the appropriate stakeholders to ensure effective management strategies

The valuation of marine ecosystem goods and services in the Wider Caribbean Region

This report provides a summary of economic analyses of marine ecosystem services in the Wider Caribbean Region for the three major marine ecosystem types being addressed by the Caribbean Large Marine Ecosystem (CLME) Project: reef, pelagic and continental shelf. Particular attention is given to empirical valuation studies. An overview of existing valuation methodologies is provided, along with recommendations for applications in the in the CLME Project area. Advantages and disadvantages of alternative methods are discussed. Market and non-market valuation studies from peer-reviewed journals, proceedings, government archives and university databases are reviewed. Attention is also given to other empirical work at the nexus of economics and marine resources in the Caribbean such as the use and effects of economic incentives, economic impact studies, and conservation finance. Studies reviewed for this report include analyses of primary and secondary data, benefits transfer applications, meta-analyses and case studies. Gaps, deficiencies and unknowns in the extant literature are highlighted and discussed. The summary and analysis of gaps together form a framework for valuation in the Wider Caribbean Region so that future work can be directed toward areas of policy importance

A management strategy for sedentary nearshore species that uses marine protected areas as a reference

Classical approaches to fisheries stock assessment rely on methods that are not conducive to managing data-poor stocks. Moreover, many nearshore rocky reef species exhibit spatial variation in harvest pressure and demographic rates, further limiting traditional stock assessment approaches. Novel management strategies to overcome data limitations and account for spatial variability are needed. With the ever-increasing implementation of no-take marine protected areas (MPAs), there is great potential for improving decision making in management through comparisons of fished populations with populations in MPAs at spatially explicit scales. We developed a management strategy that uses a combination of data-based indicators sampled inside and outside of MPAs as well as model-based reference points for data-poor, sedentary nearshore species. We performed a management strategy evaluation of this MPA-based decision tree model for a hypothetical population of grass rockfish Sebastes rastrelliger in California. We introduced process, observation, and model uncertainty in numerous scenarios and compared these scenarios with the precautionary approach currently used to manage data-poor species. Our model consistently improved total catches while maintaining the biomass and spawning potential ratio at levels well within acceptable thresholds of management. We suggest further exploration of this MPA-based management approach, and we outline a collaborative research program in the California Channel Islands that may well be suited for testing an experimental management procedure