Species associations of fifteen major commercial groundfish species in the northeastern Pacific ocean and their spatial and temporal characteristics were studied using Oregon bottom trawl logbook data, 1987 to 1993. Screening procedures were used to remove questionable data from the original logbook files, which resulted in the exclusion of information from 46% of the total available tows. Two multivariate methods, detrended correspondence analysis (DCA) and Ward's method of hierarchical cluster analysis were used to derive the association patterns of species and species groups. A general linear model that was developed for the primary DCA axis suggested that the species associations are strongly correlated with depth, but minimally correlated with the other environmental variables that were examined (latitude, season, and year). The weak correlations between DCA axis 1 and the temporal variables indicate that species associations in the study region are fairly persistent over time. The same multivariate techniques were used to examine possible sampling effects due to changes in the participating trawl vessels that contributed logbook information. Depth and latitudinal distributions of species occurrence in the logbook were similar to distributions derived from National Marine Fishery Service triennial bottom trawl survey. However, the analysis also showed that the depth coverage by the survey is not broad enough to accurately characterize associations among species that are currently subject to commercial fishing activity. / Graduation date: 1998

Two dimensional stocks of fish can be assessed with methods that mimic the analysis of research survey data but that use commercial catch-effort data. This finite population approach has scarcely been used in fisheries science though it brings about very large sample sizes of local fish density with models of only moderate levels of complexity. The extracted information about the status of the stock can be interpreted as biomass indices. Statistical inference on finite populations has been the locus of a highly specialized branch of sampling-distribution inference, unique because observable variables are not considered as random variables. If statistical inference is defined as "the identification of distinct sets of plausible and implausible values for unobserved quantities using observations and probability theory" then it is shown that Godambe's paradox implies that the classical finite populations approach is inherently contradictory as a technique of statistical inference. The demonstration is facilitated by the introduction of an extended canonical form of an experiment of chance, that apart from the three components identified by Birnbaum, also contains the time at which the experiment is performed. Realization of the time random variable leaves the likelihood function as sole data-based mathematical tool for statistical inference, in contradiction with sampling-distribution inference and in agreement with direct-likelihood and Bayesian inference. A simple mathematical model is introduced for biomass indices in the spatial field defined by the fishing grounds. It contains three unknown parameters, the natural mortality rate, the probability of observing the stock in the area covered by the fishing grounds, and mean fish density in the sub-areas where the stock was present. A new theory for the estimation of mortality rates is introduced, using length frequency data, that is based on the population ecology analogue of Hamilton-Jacobi theory of classical mechanics. The family of equations require estimations of population growth, individual growth, and recruitment pattern. Well known or new techniques are used for estimating parameters of these processes. Among the new techniques, a likelihood-based geostatistical model to estimate fish density is proposed and is now in use in fisheries science (Roa-Ureta and Niklitschek, 2007, ICES Journal of Marine Science 64:1723-1734), as well as a new method to estimate individual growth parameters (Roa-Ureta, In Press, Journal of Agricultural, Biological, and Environmental Statistics). All inference is done only using likelihood functions and approximations to likelihood functions, as required by the Strong Likelihood principle and the direct-likelihood school of statistical inference. The statistical model for biomass indices is a hierarchical model with several sources of data, hyperparameters, and nuisance parameters. Even though the level of complexity is not low, a full Bayesian formulation is not necessary. Physical factors, mathematical manipulation, profile likelihoods and estimated likelihoods are used for the elimination of nuisance parameters. Marginal normal and multivariate normal likelihood functions, as well as the functional invariance property, are used for the hierarchical structure of estimation. In this manner most sources of information and uncertainty in the data are carried over up the hierarchy to the estimation of the biomass indices.

Although strategies to meet most management objectives are relatively clearcut in single-species catchable trout programs, strategies become much more complex when two or more species are involved. A difficult problem that must be faced in evaluating catchable trout fisheries management strategies is defining management objectives. One approach to testing alternative management strategies in complex resource systems, such as catchable trout fisheries, is systems simulation. A computer-implemented catchable trout fishery simulator (CATS) was developed to evaluate fishery response under various management strategies in a multi-species stocking program. The user of CATS can select alternative management strategies and functions which generate predictions of fishing pressure on a particular fishery. To evaluate the effect of each system component, CATS was exercised over a wide range of potential system component alterations. Predominant stocking of brook trout appreciably increased average catch per angler hour and percentage return to creel. Altering the stocking ratio to favor brown trout substantially increased the number of angler hours. Stocking predominantly rainbow trout reduced the effects caused by stocking predominantly brook or brown trout. Estimates of expected angling pressure ru1d catchability coefficients of each species stocked are of primary importance because of their considerable effect on other system components. A user must have a sound objective before deciding where, when, which species, and how many fish to plant. The primary utility of CATS is to enable the user to evaluate management strategies prior to implementation. / Master of Science

My thesis examines nonlinearity between catch and effort. I use a meta-analysis of published literature and generalized linear mixed-effects models (GLMM) on both fixed and mobile gear fisheries of Atlantic Canada. The meta-analysis examines the proportionality of catch to effort using the slope of the reduced major axis (RMA) log-log regression, which accounts for “errors-in-variables”. The GLMMs explored proportionality while accounting for variation among fishing vessels. Both analyses found evidence for disproportionality between catch and effort. Catch that increases disproportionally to effort could result from either facilitation or recruitment of effort into the fishery. Catch increases that are less than proportional are expected from competitive interactions among fishers or gear saturation. The GLMM also revealed that the level of aggregation (by set, trip, monthly, or annually) can affect the apparent proportionality between catch and effort. In general, catch and effort should not be considered to be proportional. / May 2016

A main concern in fisheries science has been to identify an accurate index of fish abundance. An underlying paradigm in the science has been that the amount of effort (calculated in hours and standardized for boat size) spent fishing was the best variable to be used to account for the variation in catches. The use of the ratio, catch per unit of effort (cpue), assumes that variations in fish abundance are due to human-controlled processes above the ocean's surface. It does not account for variation due to oceanographic processes that affect fish behaviour and movement patterns below the ocean's surface. This study investigated the possibility that oceanographic factors such as temperature, salinity and depth could have effects on the variations observed in the apparent abundance of a demersal rockfish, Pacific Ocean Perch (Sebastes alutus. Gilbert). Simultaneous monitoring of physical variables and fish abundance estimation was achieved by attaching oceanographic equipment to the fishing gear of commercial vessels, monitoring the acoustic equipment and sampling the fish catch. It was found that Perch prefer a temperature range from 6.7 °C, down to at least 4.8 °C and that their movement patterns are linked to the movement of these temperatures by coastal wind patterns. Perch prefer areas with steep bathymetry, characterized by frontal activity due to interactions between the local bathymetry and tidal currents. Concerns that sampling only from highly successful commercial vessels may have biased abundance estimates, prompted the analysis of historical records of fish catch and government research surveys. Analyses between different boat sizes, different areas and different seasons from the original historical data base and a corrected subset revealed that it was mainly differences between areas that was responsible for the biasing of estimates. Deeper areas predictably produced more fish for all sizes of boats, but were fished more often by the larger boats used in the study. Therefore the field abundance estimates are likely to be biased towards areas of larger perch concentrations. / Science, Faculty of / Zoology, Department of / Graduate

The bus route survey technique is a new on-site angler survey technique that was developed for small rivers, with remote access points and low angler use. The technique employs vehicle counts to collect angler effort information. Interviews are conducted at access points to collect user characteristic and catch data from arriving, mid-trip, or departing anglers. This technique was modified to sample total recreational use on 306 km of the James River from Glen Wilton to Richmond, Virginia. The river was spatially stratified into 6 areas, two urban areas (Areas 5 and 6), and four rural areas (Areas 1-4). The two-year study was conducted from March through November, in 1988 and 1989. In order to compare the bus route technique in a large riverine system, I conducted four 4-day intensive sampling days, two weekend and two week days, in Areas 1 and 4 during each year. During these periods a complete as possible access-point survey was conducted simultaneously with the bus route survey. Surveyors for both techniques collected effort, user characteristic, and catch data from several user groups. Aerial flights were also conducted to estimate effort during the 4-day intensive sampling periods. Effort estimates of the bus route and complete access-point surveys were similar in both areas, however aerial surveys collected 205 (29%) more hours of effort per sample because it included users accessing the river through undefined or private access points. Data collected on most user characteristics were not significantly different among methods. In three of four sampling periods catch was not significantly different between the bus route and complete access-point techniques, but in 1988, Area 4, catch was statistically higher for the complete access-point surveys. To solve this problem of underestimating case with the bus route survey more afternoon samples must be conducted to intercept departing anglers. In areas with more than 15 access points or driving time between access points is longer than half the survey day, the bus route can be extended over a two-day period, or a sub-sample of a number of access points can be surveyed. A 4-day intensive sampling period was conducted in 1989, Area 1 during the summer season to compare effort, user characteristics, and catch data between two-day, sub-sampling, and complete access-point surveys. Also, 26 sampling days were conducted in 1989, Area 1 during the summer season to compare effort, user characteristics, and catch between two-day and sub-sampling bus route techniques. No significant difference in effort, and certain (9) user characteristics, or angler catch data was detected between bus route modifications or the complete access-point survey. Also, no significant differences in effort, user characteristics (11), and angler catch variables (2) were detected between the two-day and sub-sampling methods that were conducted throughout the entire summer period. The bus route survey was designed to have equal daily probabilities. When unequal daily probabilities are used, the daily effort formula becomes complex. Daily effort, user characteristics, and catch data were compared from interviews conducted in morning and afternoon samples in 1989, Area 4 during the summer season. Results showed no statistical difference in effort although a mean of 72 (52%) more hours of effort were collected per afternoon sampling period. Most user characteristics were not significantly different, but a larger proportion of departing users were interviewed in the afternoon period (54%) then the morning period (22%). Because only two departing interviews in the early sampling period were anglers, catch estimates could not be compared between the two periods. If collecting catch data is an important survey objective, then more afternoon bus route sampling periods must be conducted. / Ph. D.

Lake Liambezi in the Zambezi Region of Namibia, formerly known as the Caprivi Region, is shallow (<6m deep) and characterised by cyclic episodes of filling and drying. When full the lake supports a highly productive fishery and when dry the lake is completely dry and used for agriculture and grazing. In 2000 the lake filled, and between May 2011 and April 2012 was surveyed using beach seine, experimental gillnets and catch landing surveys to obtain information for conservation and management recommendations for the fishery. Littoral fishes in Lake Liambezi and the Kavango floodplain were sampled using seine net and physicochemical properties were measured. Seine net surveys demonstrated that Lake Liambezi littoral zones were dominated by fishes of the family Alestidae (59.7%) while Cichlids constituted the most diverse family. Juvenile Tilapia rendalli and Oreochromis macrochir were among the five most important species in the littoral zone, indicating that these commercially important species use the littoral zone as a nursery ground. Since T. rendalli and O. macrochir are commercially important species, because of this, it is advised that seine nets should not be used. Catch efficiency between monofilament and multifilament gillnets in Lake Liambezi offshore waters were assessed. Catch efficiency experimental fishing trials showed that monofilament gillnets catch per unit effort (CPUE) was three times higher than that of multifilament gillnets for Oreochromis andersonii, O. macrochir, T. rendalli, Serranochromis macrocephalus and Clarias spp. Oreochromis andersonii comprised over 66% of the overall CPUE for both net types combined indicating the importance of this species in the gillnet fishery on the lake. A fishery has been established on the lake with more than 300 canoes and 120 fishermen using monofilament and multifilament gillnets. CPUE was 15 kg/canoe/day and was significantly (P < 0.05) associated with monthly temperature and moon phase parameters indicating that the fishery of Lake Liambezi may be altered by climate and environmental factors. Annual catch from Lake Liambezi was estimated at 3193t with an estimated productivity of 106kg/ha, suggesting that Lake Liambezi makes a significant contribution to the fish supply in the Zambezi Region. Recommendations were made to manage the Lake Liambezi fishery by imposing restrictions on effort (number of fishing boats), gear type, mesh sizes and access. Proper fisheries management and monitoring should incorporate climatic and environmental factors such as temperature and moon phase to meet the challenges of global climatic changes as well as other environmental issues.

Submitted in fulfilment of the requirement for the Degree of Masters in Technology: Marketing, Durban University of Technology, 2007. / The sardine run event has been hailed as a big tourism event, yet little is known about how the sardine run affects the economy as a tourism event. Although there are numerous articles to be found on the role of tourism events in economic upliftment, very little research has been done in South Africa on this particular event, especially relating to the indigenous community involvement and the financial gain achieved from the sardine run. The study was conducted in KwaZulu-Natal (South Africa) in the Ugu districts of Hibberdene and Margate, using qualitative and quantitative research methods. The sample for the study consisted of three hundred and twenty nine respondents above the age of 16. The respondents were selected using convenience sampling and had to complete a questionnaire with the assistance of an interviewer. The objective of the research was to determine the extent to which the indigenous community's services are being marketed during the sardine run events, and how the run contributes to the economic well-being of the inhabitants of the area. The results of the research revealed that a large percentage of the respondents knew about the sardine run, with males generally having a higher awareness level than females. This finding is important because females often play a major role as breadwinners in their families. The fact that females take a less active role in the sardine run indicates an opportunity that can be exploited by those involved in the sardine run, and by local governmental and non-governmental organisations whose task it is to improve the social and economic well being of the community. The main issue was that of participation, which is low. A low participation rate has implications for skills development and reflects an opportunity for central and local government, training and educational institutions, organisations involved in the sardine run and local businesses to provide training for unemployed or under-employed youth. / M

Latitudinal patterns in reef fish assemblages reflect the influence of long-term environmental conditions, evolutionary processes and the recent, short-term influence of fishing. Long-term processes generate the typically common latitudinal patterns in reef fish assemblages, such as decreases in diversity and herbivory towards higher latitudes. These patterns reflect the global gradient in water temperature and the isolation of temperate regions from the tropics. Fishing also influences reef fish assemblages in that it decreases the abundance of large-bodied carnivore species on reefs, often leading to over-exploitation, depletion and in some cases the extirpation of populations. Indirectly, the removal of these large-bodied carnivores can influence the abundance of their prey, leading to an increase in non-target species. This study examines the latitudinal patterns in reef fish assemblages across a unique biogeographic region, the temperate Western Australian coast, and incorporates an investigation of the influence of fishing on the structure of these assemblages. Seven regions across seven degrees of latitude and seven degrees of longitude covering approximately 1500 km of coastline were sampled. Fish assemblages were characterised at each region using diver operated stereo-video transects. At each region, four locations, and within each location, four reefs were surveyed totalling 1344 transects. A significant gradient in water temperature exists with latitude and longitude. Along the Western Australian coast, and in contrast to other regions species diversity of reef fish increased towards higher latitudes and there was no evidence for a decrease in the biomass and abundance of herbivorous reef fish. The presence of the poleward flowing warm water Leeuwin current combined with the absence of major extinction events means the temperate Western Australian coast contrasts with global latitudinal trends in reef fish assemblage structure. The unique biogeographic history of temperate Western Australia has also generated a high degree of endemism among reef fish. Nearly 30 % of the species found along the west coast in this study are endemic to Western Australia, with the narrow range of these species playing an important role in the large scale patterns and spatial vi heterogeneity in reef fish assemblage structure. Furthermore, many of these endemic species are large-bodied carnivores and targeted by fishers. The impact of fishing on the abundance of large-bodied carnivores throughout the Western Australian temperate region is clear both spatially and temporally. The distribution of fishing effort is greatest along the west coast and decreases towards the south following the gradient in SST. Along the west coast, high levels of fishing effort have reduced the biomass and abundance of target carnivores to well below the standing biomass of the south coast where a low level of fishing effort occurs. This reduction in biomass is related to the historical declines in catch per unit effort (CPUE) of many key target species. These target species include endemic species such as Choerodon rubescens, Glaucosoma herbraicum, Epinephilides armatus Nemadactylus valenciennesi and Achoerodus gouldii.

Recent emphasis on linkages between essential fish habitat and fish stock productivity has raised concerns about the management of fishing activities such as trawling, which have the potential to impact fish habitat. Knowing specifically where and how intensively trawl effort has occurred over time provides ecologists with the necessary background for habitat impact and recovery studies, and provides fishery managers with an assessment of how habitat conservation objectives are being met. The objectives of this study were to (1) examine the extent to which the 2000 Pacific Fishery Management Council footrope restriction has shifted and reduced trawl fishing effort on Oregon fishing grounds, (2) to relate these changes in distribution to the benthic habitat type over which they occur, and (3) to develop methods for enhancing fine-scale spatial review of targeted fishing effort. Density analysis of available trawl start locations provided a spatial and temporal understanding of how fishing efforts increased and decreased in relation to habitat distribution and fishery management actions between 1995 and 2002. Trawl effort patterns exhibit significant inter-annual variability and patchy distribution. Areas of increased fishing effort were still evident between years, despite an overall decline in trawl tows across the time scale of this study. Tow end point locations for the years 1998-2001 were retrieved from manual logbooks for five reference sites located in the proximity of rock habitat features. Trawl towlines were mapped from start to end point and demonstrated a marked enhancement of fine-scale fishing effort resolution, with increased ability to identify effort shifts over benthic habitat. Distinct spatial shifts in fishing intensity (measured as km towed) away from rock habitat were evident at all reference sites, with an average reduction of 86%. Some slight shifts into surrounding unconsolidated sediments also occurred, indicating effort displacement as well as reduction. Fishing intensity was calculated from commercial trawl and research trawl survey towlines to achieve the most accurate assessment of fishing impacts and potential habitat recovery areas. Research trawling intensity was less than 1% of commercial trawl effort originating from the same sites. A brief comparison of Oregon vessel towlines and California vessel towlines demonstrated similar targeted fishing patterns by both fleets, except at one site. Results indicate that the footrope restriction, in conjunction with associated landing limits, was effective in protecting rocky habitats from trawl fishing impacts. Reference areas were identified where essential fish habitat (EFH) recovery is likely occurring off the coast of Oregon. Substantial regulatory changes continue in this fishery, with trip limits and gear restrictions continuously adjusted. Continued monitoring and review of spatial trawl data would assist in fishery management decision-making and assess conservation objectives for depleted groundfish and associated habitats. Future research should incorporate analysis of catch data and expand the review of trawl towlines for the entire US West coast groundfish fishery. The trawl towline spatial analysis developed in this work is a credible method for reviewing fishing effort at the scale of the fishery and in relation to detailed habitat data. The research presented here provides an example of how an interdisciplinary approach and critical assessment of data can work to resolve marine management challenges. / Graduation date: 2004