The a4a Assessment Model - Model description and testing

A BSTRACT. This study describes the growth parameters of the blue crab males Callinectes arcuatus Ordway, 1863 based on samples from a coastal lagoon in the southern Gulf of California and from individual nurtured under controlled conditions. The models assessed were Schnute growth models with the four variants and special case for the von Bertalanffy (VBGM). The criterion used to select the best model was the Akaike information criterion (AIC). The best models fitted were the case 3 of Schnute model for separate data set, wild or reared indicating a linear growth, but combined data set fitted better to the VBGM function, case 5, suggesting an asymptotic growth of the C. arcuatus . We are aware that our result depends of the acceptance that recreation of the entire period of growth came from reared and fished individuals. Our conclusions are in ways 1) to model growth by treating cohorts as individuals yield in good estimations of k and the L∞ equivalent that can be used directly in stock assessment models, and 2) the ranges of validity of the best growth models for blue crabs C. arcuatus growing in wild environments and culture environment overlapped in the range of 62 mm to 85 mm of CW but they have a continuity that recreates the blue crab growth throughout their entire period of life.

The thermophily, fishing season and central fishing ground of Japanese pilchard (Sardinops melanosticta) were studied by using satellite remote sensing (SRS) and other methods in Haizhou Bay and Tsushima waters during 1986-1990. A rapid prediction method of fishing ground is presented. Moreover, the results indicated that the thermophilic values of the fish stock are 11-20 degrees C and both fishing grounds are in increasing temperature process from the beginning to the end of the fishing period. The Japanese pilchards gather vigorously at the sea surface temperature of 15-17 degrees C. The water temperature is a key factor affecting the fishing season and the catch of the fishing ground. The increasing temperature process restricts the fishing season development and central fishing ground formation. The accuracy of 15 predictions made in the Haizhou Bay fishing ground is up to 91.3%, and 37 predictions made in the Tsushima, fishing ground shorten the fish detection time by 13.4% - 22% on the average.

Integrating the standardization of catch-per-unit-of-effort into stock assessment models: testing a population dynamics model and using multiple data types

Spatial Structure: Theory, estimation and application in stock assessment models

We estimated the economic benefits of the Chesapeake Bay TMDL to commercial fish harvesters and consumers, recreational anglers, and other outdoor recreators. To forecast the impacts of the TMDL on harvested fish and shellfish stocks in the bay and connected Atlantic coast waters, we used a summary of judgments from an expert panel and a multi-species model of Chesapeake Bay fisheries. We estimated benefits to consumers in commercial fish markets using a multi-stage inverse demand system, which models price as a function of exogenous supply and accounts for substitution possibilities between 13 different species and as many as five regions. Models were estimated using monthly harvest data from the years 1991 to 2011. The estimated parameters of the inverse demand systems were then used to calculate compensating and equivalent variation from the changes in harvests between the baseline and TMDL scenarios. To estimate producer surplus changes, we assumed that fishing effort will remain fixed at recent levels in each fishery, so harvesting costs do not increase due to the TMDL. The resulting estimates of commercial fishing benefits range between $3 and $26 million per year. We also examined the implications of alternative assumptions about the management regime in each fishery, including fixed effort, open access, and maximum sustainable surplus. We calculated benefits to recreational anglers using a linked participation and site-choice recreation demand model. The model was estimated using angler intercept survey data from the Marine Recreational Fisheries Statistics Survey (MRFSS). Catch rates were calculated using historic reported catch from the MRFSS. We accounted for the sample selection bias caused by the non-random intercept survey sampling design using weights based on historic visitation frequencies at each intercept site. The intercept data were used to estimate a random utility site-choice model, and counts of trips from respondent zip codes were used to estimate a negative binomial participation model conditional on the inclusive value of all sites as estimated by the site-choice model. The resulting estimates of recreational fishing benefits range between $5 and $59 million per year. We used a separate recreation demand model to estimate the benefits associated with other outdoor recreation activities. The model was estimated using aggregate data on the total number of visitors to national and state parks in Maryland, Virginia, and Delaware. The aggregate visitation data alone are insufficient to estimate all parameters of the model, so these data were supplemented with survey data on the number of recreation trips taken to the Chesapeake Bay collected from a random sample of individuals in the study area. The marginal effects of water quality on recreators’ site choices were estimated in a second-stage regression, using estimates of site-specific constants from the first-stage site-choice model as the dependent variable and measures of average water quality conditions and other fixed site attributes as explanatory variables. The central estimates of the outdoor recreation benefits (exclusive of recreational fishing) are between $105 to $280 million per year.

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 thorough comparison of derived yield streams between empirical MPs and stock assessment models has not been explored. We first evaluate trade-offs in conservation and yield metrics for data-limited approaches through management strategy evaluation (MSE) of seven data-rich reef fish species in the Gulf of Mexico. We then apply data-limited approaches for each species and compare how catch advice differs from current age-based assessment models. MSEs identified empirical MPs (e.g., using relative abundance) as a compromise between data requirements and the ability to consistently achieve management objectives (e.g., prevent overfishing). Catch advice differed greatly among data-limited approaches and current assessments, likely due to data inputs and assumptions. Adaptive MPs become clearly viable options that can achieve management objectives while incorporating auxiliary data beyond catch-only approaches.

Incorporating fecundity into stock assessment models may improve stock assessment and management of Bristol Bay red king crab Paralithodes camtschaticus. To do this, the size—fecundity relationship for the population must be established, including variability due to female reproductive state. In 2012, egg clutches were collected from red king crab in Bristol Bay, AK, and individual fecundity was estimated. Best evidence suggests small females were primiparous (brooding first egg clutch), which provided the opportunity to compare estimated fecundity of primiparous and multiparous (brooding second or subsequent egg clutch) females. In the best-fit model, fecundity increased with female size and below 108.8 mm carapace length (CL) the slope of the size—fecundity relationship decreased by 27%.Multiparous females were 28%–30% more fecund than primiparous females of the same size. If managers incorporate fecundity into stock assessment models, the differences in fecundity between primiparous and multiparous females should be considered, otherwise population fecundity will be overestimated if the size—fecundity relationship of only multiparous females is used in the calculations because of the differences in fecundity between primiparous and multiparous females of the same size.

Quickly accessing the contents of a video is challenging for users, particularly for unstructured video, which contains no intentional shot boundaries, no chapters, and no apparent edited format. We approach this problem in the domain of lecture videos though the use of machine learning, to gather semantic information about the videos; and through user interface design, to enable users to fully utilize this new information. First, we use machine learning techniques to gather the semantic information. We develop a system for rapid automatic semantic tagging using a heuristic-based feature selection algorithm called Sort-Merge, by using large initial heterogeneous low-level feature sets (cardinality greater than 1K). We explore applying Sort-Merge to heterogeneous feature sets though two methods: early fusion and late fusion. Each takes different approaches to handling the different kinds of features in the heterogeneous set. We determine the most predictive feature sets for key-frame filters such as “has text”, “has computer source code”, or “has instructor motion”. Specifically we explore the usefulness of Harr Wavelets, Fast Fourier Transforms, Color Coherence Vectors, Line Detectors, Ink Features and Pan/Tilt/Zoom detectors. For evaluation, we introduce a “keeper” heuristic for feature sets, which provides a method of performance comparison against a baseline. Second, we create a user interface to allow the user to make use of the semantic tags we gathered though our computer vision and machine learning process. The interface is integrated into an existing video browser, which detected shot-like boundaries and presented a multitimeline view. The content within shot-like boundaries is represented by frames to which our new interface applies the generated semantic tags. Specifically, we make accessible the semantic concepts of 'text', 'code', 'presenter', and 'person motion.' The tags are detected in the simulated shots using the filters generated with our machine learning approach and are displayed to users using a user-customizable multi-timeline view. We also generate tags based on ASRgenerated transcripts that have been limited to the words provided in the index of the course text book. Each of these occurrences is aligned with the simulated shots. Each spoken word becomes a tag analogous to the visual concepts. A full Boolean algebra over the tags is provided to enable new composite tags such as 'text or code, but no presenter.' Finally, we quantify the effectiveness of our features and our browser through user studies, both observational and task driven. We find that users that use the full suite of tools performed a search task in 60% of the time of users without access to tags. We find that when users are asked to perform search tasks they follow a nearly fixed pattern of accesses, alternating between the use of tags and Keyframes, or between the use of Word Bubbles and the media player. Based on user behavior and feedback, we redesigned the interface to group spatially interface components that are used together, removed un-used components, and redesigned the display of Word Bubbles to match that of the Visual Tags. We found that users strongly preferred the Keyframe tool, as well as both kinds of tags. Users also either found the algebra very useful or not useful at all.

Natural or hydraulic fractures are of major importance for the productivity of hydrocarbon reservoirs. Besides fracture detection, also the aperture and extension of the fractures are essential for a correct reservoir productivity estimate. There are many ways to detect and measure fractures, such as borehole televiewers and electrical borehole scans. A practical approach to investigate fracture properties is by means of acoustic logging. In this thesis, borehole waves along fractured media are investigated theoretically and experimentally. Theoretically, the effect of a fracture intersecting a vertical borehole can be described by the introduction of a frequency-dependent (dynamic) borehole fluid compressibility which is measured in the laboratory. The dynamic fluid bulk modulus comprises the intrinsic fluid stiffness, the borehole wall distensibility, and the radial fluid seepage into the adjacent (horizontal) permeable zones. The latter two effects tend to diminish the intrinsic fluid’s stiffness, giving rise to a lower effective bulk modulus amplitude and thus to a lower wave speed in the borehole. The radial oscillatory fluid seepage causes viscous friction in the adjacent zones and results in a phase lag between the pressure increase and the compression of the borehole fluid, leading to attenuation of the borehole waves. This seepage effect is expressed in terms of a so-called borehole dynamic wall impedance specifying the radial fluid velocity at the borehole wall as a function of the borehole pressure variations. If a borehole wave travels down from an undamaged zone into a fracture zone, it will encounter an impedance contrast causing the wave to partially reflect and partially transmit, thus revealing the presence of permeable fracture zone adjacent to the borehole. Stoneley wave propagation in porous and fractured formations is studied experimentally by means of a vertical shock tube facility. In this set-up, shock waves in air are generated that travel downwards into a water-saturated cylindrical rock sample that has a borehole drilled along the center axis. In this way, high-energy borehole waves can be generated with excellent repeatability. A logging probe is installed in the borehole to measure the pressure profiles. Reflection from the water-sample interface and from the free water interface can be recorded by means of a fixed pressure transducer mounted in the wall of the shock tube above the sample in the water layer. The fractures in the formation are represented by small horizontal slits in composite cylinders whose upper and lower parts are separated by small spacer poles. In this way, a variable horizontal fracture (slit) aperture can be obtained. Obviously these fractures form an open connection between the borehole fluid and the fluid outside the cylinder. Also mandrel samples are used for horizontal slits that are not open to the fluid outside the cylinder, thus representing fractures with finite radial extension. Wave experiments show that varying fracture widths significantly alter the recorded Stoneley wave pressure signal at fixed depth. The reflection and transmission of borehole tube waves over 1 and 5 mm fractures are correctly predicted by theory. Other wave experiments show that attenuation in boreholes adjacent to porous zones without fractures can be predicted by theory. This technique even allows a direct measurement of the permeability, although the acoustically measured permeability and the permeability measured by falling-head technique still show a significant discrepancy. This technique is directly applicable to fractured porous reservoir core samples.

The present study was carried out in the rice-wheat area of Pakistani Punjab. The data for the study was collected from three main districts of central Punjab Province i.e. Gujranwala, Sheikhupura and Hafizabad. In total 234 farmers were interviewed. The impact of agricultural extension services was estimated on adoption of new improved technologies and crop yields. The propensity score matching approach for impact evaluation was employed in the current study to correct for potential sample selection biasedness that may arise due to systematic differences between the farmers having benefited from agricultural extension services and not benefited from agricultural extension services. The empirical results indicate that agricultural extension services play a significant role in adoption of improved agricultural technologies like laser leveling, rice and wheat varieties. The farmers having benefitted from agricultural extension services were also getting higher rice and wheat yields. The results also indicates that mostly the large farmers are getting benefits from agricultural extension services and small scale farmers have less access to agricultural extension services.

Marine recreational fishing (MRF) is a popular outdoor activity that contributes substantially to total harvest in many coastal stocks, yet it is rarely integrated into stock assessments and its impact on target stocks is often unknown. For the red-listed European lobster ( Homarus gammarus ) in Norway , we applied two probabilistic off-site survey methods (diary and recall) to estimate participation, effort, harvest rates and total harvest across regions. The effects of accounting for MRF were then evaluated in a stock assessment model. The recall method achieved higher response rates and resulted in slightly lower harvest estimates than the diary survey. When combined with a mandatory national registration system, these methods enabled cost-efficient and representative estimation of total harvest. Recreational fishers accounted for 71–90% of total lobster removals, confirming their dominant role in the fishery. If recreational harvest was not accounted for, the stock status was overestimated, while current fishing pressure was significantly underestimated. Our findings demonstrate that excluding MRF can mask unsustainable exploitation of an overexploited stock and hinder effective management. We show that combining registration with low-burden methods provides practical and reliable foundation for incorporating MRF into stock assessments, a first step towards achieving sustainable coastal fisheries management. Graphical abstract

The stock assessment model for the Antarctic krill fishery is a population model operating on daily timesteps, which permits modeling within‐year patterns of some population dynamics. We explored the effects of including within‐year patterns in natural and fishing mortality on catch limits of krill, by incorporating temporal presence of key predator species and contemporary temporal trends of the fishing fleet. We found that inclusion of within‐year variation in natural and fishing mortalities increased catch limits. Fishing mortality had a greater effect than natural mortality despite differences in top‐down predation on krill, and potentially increased catch limits by 24% compared to the baseline model. Additionally, the stock assessment model allowed a higher catch limit when fishing was during peak summer months than autumn. Number of days with active fishing was negatively related to precautionary catch limits. Future stock assessments should incorporate contemporary spatiotemporal fishing trends and consider implementing additional ecosystem components into the model.

A separable catch-age stock assessment model that accommodates predation mortality is applied to the Gulf of Alaska walleye pollock (Theragra chalcogramma) assessment. Three predators are incorporated in the model: arrowtooth flounder (Atheresthes stomias), Pacific halibut (Hippoglossus stenolepis), and Steller sea lion (Eumetopias jubatus). The effect of these predators is examined by defining the predation mortality as a type of fishery. The model is used to quantify changes in the relative fit to the survey, fishery, and predator data when the assumption of constant natural mortality is relaxed. Specifically, we examine the effect of assumptions regarding the functional feeding response, residual naturaly mortality, and uncertainty in predator biomass on stock assessment. Total natural mortality rates (including predation) tended to be higher than estimated from life history characteristics of the stock. Models that did not account for uncertainty in natural mortality underestimated uncertainty in current stock biomass by as much as 20%. Our results indicate that independent estimates of survey selectivity, additional food habits data, and estimates of the feeding responses of predators to different prey densities are all needed to improve our ability to develop stock assessment models that address ecosystem concerns. 2000 International Council for the Exploration of the Sea

Conventional stock assessment models require large amounts of historical catch and effort data, which are often unavailable for small-scale fisheries such as the blue swimming crab ( Portunus pelagicus ) fishery on the east coast of Aceh. The lack of stock assessment models applicable to many fish species with limited data, such as the BSC, has hindered policymakers' ability to monitor fish stock status more effectively. When historical catch data, abundance indices, or age-composition data are unavailable, stock assessment methods can be employed using size and/or life history information. This study aimed to determine the stock status of P. pelagicus using limited data, focusing on the length-based spawning potential ratio. Data were collected periodically at several crab landing sites along the eastern coast of Aceh. Based on the life history parameters analyzed, the crab stock was categorized as overexploited (red flag), with an SPR < 0.2 (20%). In line with this assessment, the crab exploitation ratio ( F / M ) was high at 1.85, with an exploitation rate ( E ) of 0.71, indicating overfishing. Management actions to reduce crab fishing effort are necessary to improve the status of the stock and achieve a healthier stock.

The Bayesian approach to stock assessment determines the probabilities of alternative hypotheses using information for the stock in question and from inferences for other stocks/species. These probabilities are essential if the consequences of alternative management actions are to be evaluated through a decision analysis. Using the Bayesian approach to stock assessment and decision analysis it becomes possible to admit the full range of uncertainty and use the collective historical experience of fisheries science when estimating the consequences of proposed management actions. Recent advances in computing algorithms and power have allowed methods based on the Bayesian approach to be used even for fairly complex stock assessment models and to be within the reach of most stock assessment scientists. However, to avoid coming to ill-founded conclusions, care must be taken when selecting prior distributions. In particular, selection of priors designed to be noninformative with respect to quantities of interest to management is problematic. The arguments of the paper are illustrated using New Zealand's western stock of hoki, Macruronus novaezelandiae (Merlucciidae) and the Bering--Chukchi--Beaufort Seas stock of bowhead whales as examples