ゼロの多いデータの解析：負の２項回帰モデルによる傾向の過大推定

要旨あり環境リスクと統計解析 －データ基盤構築と解析－原著論

Marine Reserve Design: Optimal Size, Habitats, Species Affinities, Diversity, And Ocean Microclimate

The design of marine reserves is complex and fraught with uncertainty. However, protection of critical habitat is of paramount importance for reserve design. We present a case study as an example of a reserve design based on fine-scale habitats, the affinities of exploited species to these habitats, adult mobility, and the physical forcing affecting the dynamics of the habitats. These factors and their interaction are integrated in an algorithm that determines the optimal size and location of a marine reserve for a set of 20 exploited species within five different habitats inside a large kelp forest in southern California. The result is a reserve that encompasses similar to 42% of the kelp forest. Our approach differs fundamentally from many other marine reserve siting methods in which goals of area, diversity, or biomass are targeted a priori. Rather, our method was developed to determine how large a reserve must be within a specific area to protect a self-sustaining assemblage of exploited species. The algorithm is applicable across different ecosystems, spatial scales, and for any number of species. The result is a reserve in which habitat value is optimized for a predetermined set of exploited species against the area left open to exploitation. The importance of fine-scale habitat definitions for the exploited species off La Jolla is exemplified by the spatial pattern of habitats and the stability of these habitats within the kelp forest, both of which appear to be determined by ocean microclimate

Review of potential line-transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific

A twelve-year hiatus in fishery-independent marine mammal surveys in the eastern tropical Pacific Ocean (ETP), combined with a mandate to monitor dolphin stock status under international agreements and the need for reliable stock status information to set dolphin bycatch limits in the tuna purse-seine fishery, has renewed debate about how best to assess and monitor ETP dolphin stock status. The high cost of replicating previous ship-based surveys has intensified this debate. In this review, transect methods for estimating animal abundance from dedicated research surveys are considered, with a focus on both contemporary and potential methods suitable for surveying large areas for dolphin species that can form large, multi-species aggregations. Covered in this review are potential improvements to the previous ship-based survey methodology, other ship-based methods, alternative approaches based on high-resolution imagery and passive acoustics, and combinations of ship-based and alternative approaches. It is concluded that for immediate management needs, ship-based surveys, with some suggested modifications to improve precision, are the only reliable option despite their high cost. However, it is recommended that a top research priority should be development of composite methods. Pilot studies on the use of high-resolution imagery and passive acoustics for development of indices of relative abundance to be used in composite methods should be part of any future ship-based survey efforts

Statistical Learning Procedures for Monitoring Regulatory Compliance: An Application to Fisheries Data

As a special case of statistical learning, ensemble methods are well suited for the analysis of opportunistically collected data that involve many weak and sometimes specialized predictors, especially when subject-matter knowledge favors inductive approaches. In this paper, we analyze data on the incidental mortality of dolphins in the purse-seine fishery for tunas in the eastern Pacific Ocean. The goal is to identify those rare purse-seine sets for which incidental mortality would be expected but none was reported. The ensemble method random forests is used to classify sets according to whether mortality was (response = 1) or was not (response = 0) reported. To identify questionable reporting practice, we construct “residuals” as the difference between the categorical response (0, 1) and the proportion of trees in the forest that correctly assify a given set. Two uses of these residuals to identify suspicious data are illustrated. This approach shows promise as a means to identify suspect data gathered for environmental monitoring

Statistical Learning Procedures for Monitoring Regulatory Compliance: An Application to Fisheries Data

As a special case of statistical learning, ensemble methods are well suited for the analysis of opportunistically collected data that involve many weak and sometimes specialized predictors, especially when subject-matter knowledge favors inductive approaches. In this paper, we analyze data on the incidental mortality of dolphins in the purse-seine fishery for tunas in the eastern Pacific Ocean. The goal is to identify those rare purse-seine sets for which incidental mortality would be expected but none was reported. The ensemble method random forests is used to classify sets according to whether mortality was (response = 1) or was not (response = 0) reported. To identify questionable reporting practice, we construct "residuals" as the difference between the categorical response (0, 1) and the proportion of trees in the forest that correctly classify a given set. Two uses of these residuals to identify suspicious data are illustrated. This approach shows promise as a means to identify suspect data gathered for environmental monitoring

Effects of gear characteristics on the presence of bigeye tuna (Thunnus obesus) in the catches of the purse-seine fishery of the eastern Pacific Ocean. (submitted ICES Journal of Marine Science

Effects of gear characteristics on the presence of bigeye tuna (Thunnus obesus) in the catches of the purse-seine fishery of the eastern Pacific Ocea

obesus) in the catches of the purse-seine fishery of the eastern Pacific Ocean

Overfishing of bigeye tuna in the eastern Pacific Ocean has motivated a search for pratical means of reducing bigeye catch. We develop a classification algorithm for the presence/absence of bigeye in purse-seine sets on floating objects, the dominant mode of purse-seining for bigeye, using the tree-based method random forests to explore the effects of gear characteristics. Although the location of the set was the strongest determinant of the presence of bigeye catch with these data, in some areas, bigyeye were more likely to be caught on floating objects with greater underwater depths and with deeper purse-seine nets. Misclassified sets were found to be concentrated within certain vessels, suggesting that the existence of additional ‘vessel effects ’ on the presence of bigeye which may be amenable to further study. Results indicate that fishermen can avoid catching bigeye in some areas by changing the depth of the material hanging from the floating object and the actual fishing depth of the net, or by moving to other fishing areas. However, we believe that the complex nature of gear and environmental interactions, and the impact of gear restrictions on the catches of tuna species other than bigeye, argu

The Ecuadorian Artisanal Fishery for Large Pelagics: Species Composition and Spatio-Temporal Dynamics

<div><p>The artisanal fisheries of Ecuador operate within one of the most dynamic and productive marine ecosystems of the world. This study investigates the catch composition of the Ecuadorian artisanal fishery for large pelagic fishes, including aspects of its spatio-temporal dynamics. The analyses of this study are based on the most extensive dataset available to date for this fishery: a total of 106,963 trip-landing inspection records collected at its five principal ports during 2008 ‒ 2012. Ecuadorian artisanal fisheries remove a substantial amount of biomass from the upper trophic-level predatory fish community of the eastern tropical Pacific Ocean. It is estimated that at least 135 thousand metric tons (mt) (about 15.5 million fish) were landed in the five principal ports during the study period. The great novelty of Ecuadorian artisanal fisheries is the “oceanic-artisanal” fleet component, which consists of mother-ship (<i>nodriza</i>) boats with their towed fiber-glass skiffs (<i>fibras</i>) operating with pelagic longlines. This fleet has fully expanded into oceanic waters as far offshore as 100°W, west of the Galapagos Archipelago. It is estimated that <i>nodriza</i> operations produce as much as 80% of the total catches of the artisanal fishery. The remainder is produced by independent <i>fibra</i>s operating in inshore waters with pelagic longlines and/or surface gillnets. A multivariate regression tree analysis was used to investigate spatio-environmental effects on the <i>nodriza</i> fleet (n = 6,821 trips). The catch species composition of the <i>nodriza</i> fleet is strongly influenced by the northwesterly circulation of the Humboldt Current along the coast of Peru and its associated cold waters masses. The target species and longline gear-type used by <i>nodrizas</i> change seasonally with the incursion of cool waters (< 25°C) from the south and offshore. During this season, dolphinfish (<i>Coryphaena hippurus</i>) dominates the catches. However, in warmer waters, the fishery changes to tuna-billfish-shark longline gear and the catch composition becomes much more diverse.</p></div