Evaluating the efficacy of managing West Coast groundfish resources through simulations

Management of West Coast groundfish resources by the Pacific Fishery Management Council involves Federal government and academic scientists conducting stock assessments, generally using the stock synthesis framework, applying the 40-10 rule to determine harvest guidelines for resources that are not overfished and conducting rebuilding analyses to determine harvest guidelines for resources that have been designated as overfished. However, this management system has not been evaluated in terms of its ability to satisfy the National Standard 1 goals of the Sustainable Fisheries Act. A Monte Carlo simulation framework is therefore outlined that can be used to make such evaluations. Based on simulations tailored to a situation similar to that of managing the widow rockfish (Sebastes entomelas) resource, it is shown that catches during recovery and thereafter are likely to be highly variable (up to ±30% from one year to the next). Such variability is far greater than has been presented to the decision makers to date. Reductions in interannual variability in catches through additional data collection are, however, unlikely. Rather, improved performance will probably arise from better methods for predicting future recruitment. Rebuilding analyses include quantities such as the year to which the desired probability of recovery applies. The estimates of such quantities are, however, very poorly determined

Can We Stabilize Fisheries' Benefits from a Fluctuating Stock? A Bioeconomic Assessment of The Pacific Whiting Fishery

Pacific whiting (Merluccius productus) is one of the most commercially valuable fish species in the Pacific coast groundfish fishery, experiences extreme variability in annual recruitment. This variability causes fluctuations in stock abundance and subsequent catch and economic benefits. This study develops a stochastic bioeconomic model of the Pacific whiting fishery in order to assess various fishing strategies based upon economic and biological criteria. The stochastic fisheries model relies on a hockey-stick recruitment function with wide variance, generating occasional extremely large recruitment. In response to stock variability, we examine linear harvest strategies which close the fishery when estimated biomass falls below a stipulated given minimum biomass level (B[min]), and set catch quotas as a fraction of surplus of existing biomass above the minimum biomass level (B[y]-B[min]). To simulate the variability of results from each strategy we performed 1,000 50-year simulations. The results are summarized as average and variance of annual harvest, biomass and 50-year Net Present Values (NPV) for the fishery. This study concludes that the harvest strategy with low minimum biomass (5% of unfished biomass) and low fraction (0.2) would be desirable for three reasons: (1) maximization of NPV, (2) stochastic dominance and (3) biomass conservation.Keywords: bioeconomics, Fisheries Economics, fluctuating fish stock, stochastic model, Theoretical and Empirical Bio-Economic Analysis, Pacific whiting fisheryKeywords: bioeconomics, Fisheries Economics, fluctuating fish stock, stochastic model, Theoretical and Empirical Bio-Economic Analysis, Pacific whiting fisher

Impacts of Vessel Capacity Reduction Programs on Efficiency in Fisheries: the Case of Australia's Multispecies Northern Prawn Fishery

Capacity reduction programs in the form of buybacks or decommissioning programs have had relatively widespread application in fisheries in the US, Europe and Australia. A common criticism of such programs is that they remove the least efficient vessels first, resulting in an increase in average efficiency of the remaining fleet. The effective fishing power of the fleet, therefore, does not decrease in proportion to the number of vessels removed. Further, reduced crowding may increase efficiency of the remaining vessels. In this paper, the effects of a buyback program on average technical efficiency in Australia’s Northern Prawn Fishery are examined using a multi-output distance function approach with an explicit inefficiency model. The results indicate that average efficiency of the remaining vessels was greater than that of the removed vessels, and that average efficiency of remaining vessels also increased as a result of reduced crowding.Keywords: Fishing Capacity and Buyback Programs, Fisheries Economics, Fish and Aquaculture Sectors Developmen

Evaluation of Continuous Tumor-Size-Based End Points as Surrogates for Overall Survival in Randomized Clinical Trials in Metastatic Colorectal Cancer

IMPORTANCE: Tumor measurements can be used to estimate time to nadir and depth of nadir as potential surrogates for overall survival (OS). OBJECTIVE: To assess time to nadir and depth of nadir as surrogates for OS in metastatic colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS: Pooled analysis of 20 randomized clinical trials within the Aide et Recherche en Cancerologie Digestive database, which contains academic and industry-sponsored trials, was conducted. Three sets of comparisons were performed: chemotherapy alone, antiangiogenic agents, and anti–epidermal growth factor receptor agents in first-line treatment for patients with metastatic colorectal cancer. MAIN OUTCOMES AND MEASURES: Surrogacy of time to nadir and depth of nadir was assessed at the trial level based on joint modeling of relative tumor-size change vs baseline and OS. Treatment effects on time to nadir and on depth of nadir were defined in terms of between-arm differences in time to nadir and in depth of nadir, and both were assessed in linear regressions for their correlation with treatment effects (hazard ratios) on OS within each set. The strengths of association were quantified using sample-size–weighted coefficients of determination (R2), with values closer to 1.00 indicating stronger association. At the patient level, the correlation was assessed between modeled relative tumor-size change and OS. RESULTS: For 14 chemotherapy comparisons in 4289 patients, the R2 value was 0.63 (95% CI, 0.30-0.96) for the association between treatment effects on time to nadir and OS and 0.08 (95% CI, 0-0.37) for depth of nadir and OS. For 11 antiangiogenic agent comparisons (4854 patients), corresponding values of R2 were 0.25 (95% CI, 0-0.72) and 0.06 (95% CI, 0-0.35). For 8 anti–epidermal growth factor receptor comparisons (2684 patients), corresponding values of R2 were 0.24 (95% CI, 0-0.83) and 0.21 (95% CI, 0-0.78). CONCLUSIONS AND RELEVANCE: In contrast with early reports favoring depth of response as a surrogate, these results suggest that neither time to nadir nor depth of nadir is an acceptable surrogate for OS in the first-line treatment of metastatic colorectal cancer

Adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC) in patients with colon cancer at high risk of peritoneal carcinomatosis; the COLOPEC randomized multicentre trial

Background: The peritoneum is the second most common site of recurrence in colorectal cancer. Early detection of peritoneal carcinomatosis (PC) by imaging is difficult. Patients eventually presenting with clinically apparent PC have a poor prognosis. Median survival is only about five months if untreated and the benefit of palliative systemic chemotherapy is limited. Only a quarter of patients are eligible for curative treatment, consisting of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CR/HIPEC). However, the effectiveness depends highly on the extent of disease and the treatment is associated with a considerable complication rate. These clinical problems underline the need for effective adjuvant therapy in high-risk patients to minimize the risk of outgrowth of peritoneal micro metastases. Adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC) seems to be suitable for this purpose. Without the need for cytoreductive surgery, adjuvant HIPEC can be performed with a low complication rate and short hospital stay. Methods/Design: The aim of this study is to determine the effectiveness of adjuvant HIPEC in preventing the development of PC in patients with colon cancer at high risk of peritoneal recurrence. This study will be performed in the nine Dutch HIPEC centres, starting in April 2015. Eligible for inclusion are patients who underwent curative resection for T4 or intra-abdominally perforated cM0 stage colon cancer. After resection of the primary tumour, 176 patients will be randomized to adjuvant HIPEC followed by routine adjuvant systemic chemotherapy in the experimental arm, or to systemic chemotherapy only in the control arm. Adjuvant HIPEC will be performed simultaneously or shortly after the primary resection. Oxaliplatin will be used as chemotherapeutic agent, for 30 min at 42-43 degrees C. Just before HIPEC, 5-fluorouracil and leucovorin will be administered intravenously. Primary endpoint is peritoneal disease-free survival at 18 months. Diagnostic laparoscopy will be performed routinely after 18 months postoperatively in both arms of the study in patients without evidence of disease based on routine follow-up using CT imaging and CEA. Discussion: Adjuvant HIPEC is assumed to reduce the expected 25 % absolute risk of PC in patients with T4 or perforated colon cancer to a risk of 10 %. This reduction is likely to translate into a prolonged overall survival

Modelling the economic and ecological impacts of the transition to individual transferable quotas in the multispecies US west coast groundfish trawl fleet

There is a need to understand the potential impacts on ecosystems and economies from shifting fisheries management towards individual transferable quota (ITQ) programmes. Multispecies fisheries present the challenge of understanding spatial patterns in fisher behaviour as they strive to balance profitable target catches while avoiding species with low catch limits. A spatially explicit model of biological and fleet dynamics was constructed to evaluate how the limited-entry groundfish trawl fleet off the US west coast and selected groundfish species (targeted Dover sole, and overfished darkblotched rockfish) were affected by two approaches to management: trip limits and ITQs. The model includes regional populations for both species, provides biological and socio-economic outputs, and determines quota price endogenously when applied for ITQs. Under ITQ management, effort and the total landings of the overfished species, darkblotched rockfish, were lower, coastwide profits higher, and the centre of fishing activity shifted south to areas with lower landing rates of darkblotched rockfish. The framework presented holds promise for obtaining insight about how new, untested management alternatives affect coastal and marine resources and those who rely on them

Optimal vessel size and output in the Australian northern prawn fishery: a restricted profit function approach

Individual transferable quotas (ITQs) are to be introduced into Australia’s Northern Prawn fishery in the near future. Total allowable catches (TACs) are to be set with the objective of maximising economic efficiency in the fishery. Under ITQs, vessel owners have the ability to adjust their fishing activities to maximise profits and changes in fleet structure resulting from management changes need to be considered when determining TACs. A restricted profit function for the fishery was estimated to determine the optimal vessel characteristics and output levels as a guide to how the fleet may adjust under an ITQ system. Vessels were found to be currently close to their optimal size given average historic prices and current stock conditions. However, higher tiger prawn stocks are expected to result in the average size of vessels increasing, with rising fuel prices also likely to result in capital being substituted for fishing days. Optimal average vessel-level catches of the main species are lower than current average vessel catches for a wide range of input and output prices. These changes in vessel characteristics and behaviour need to be incorporated in the derivation of the optimal TACs if economic efficiency objectives are to be achieved

Bayesian fishable biomass dynamics models incorporating fished area and relative fish density

Fisheries typically experience large changes over time in fishing effort. The size of the area fished may also change substantially over time, mimicking the trend in fishing effort, and may have major effects on the population dynamics and fishing process. We extend a biomass dynamics model to incorporate fished area and relative fish density in fished and unfished areas. The fishable population is defined as those individuals in the fished area and those that are sufficiently close to the fished area that they could potentially move into fished area during the fishing season. We estimate fishable biomass using three models assuming different level of population mixing between fished and unfished areas (i.e., partial mixing, full mixing, and no mixing). The models are implemented within a hierarchical Bayesian framework. Model performance is explored using simulations, and the approach is illustrated using logbook data for two tiger prawn species in Australia's Northern Prawn Fishery. The partial mixing model that involves estimating a mixing parameter performs better than the models that assume no or full mixing. The methods could be applied to other fisheries where the area fished has changed substantially over the history of the fishery