301 research outputs found
Simultaneous Perturbation Algorithms for Batch Off-Policy Search
We propose novel policy search algorithms in the context of off-policy, batch
mode reinforcement learning (RL) with continuous state and action spaces. Given
a batch collection of trajectories, we perform off-line policy evaluation using
an algorithm similar to that by [Fonteneau et al., 2010]. Using this
Monte-Carlo like policy evaluator, we perform policy search in a class of
parameterized policies. We propose both first order policy gradient and second
order policy Newton algorithms. All our algorithms incorporate simultaneous
perturbation estimates for the gradient as well as the Hessian of the
cost-to-go vector, since the latter is unknown and only biased estimates are
available. We demonstrate their practicality on a simple 1-dimensional
continuous state space problem
La pêche crevettière en Côte d'Ivoire. Bilan 1969-1970 et perspectives
The evolution of the fishery of the pink shrimp Penaeus duorarum Burkenroad is analysed from its beginning in 1969 until the end of 1970. A rapid and general decline of the yield has been evident during this period. The actual shrimp fleet seems to be too big to allow an exploitation economically convenient of the stock
La pêche au chalut en Côte d'Ivoire. Maximum de rendement économique
This paper analyses the relations between effort and catch per unit effort of trawlers which worked in Côte d'Ivoire from Jan 1966 to Dec 1970. A fishing effort permitting to exploit fishery in the best rentability conditions is proposed
GEOGRAPHICAL VARIABILITY IN THE AMOUNT OF BIGEYE CAUGHT UNDER FADS BY PURSE SEINERS IN THE EASTERN ATLANTIC: FROM THE MULTISPECIES SAMPLES AND THE ICCAT STATISTICS
This paper analyses the geographical distribution of bigeye FAD catches by PS using results of
multispecies sampling of EU FAD catches (1991-2016). This analysis shows marked
geographical gradients in the geographical distribution of bigeye catches, catches being rare in
coastal areas and increasingly abundant at increasing distances from the shore. Opposite
changes are observed for yellowfin abundance, while skipjack abundance tends to be similar in
most areas. Yearly trends in relative abundances of bigeye and skipjack are also observed. These
observed species compositions are widely in contradiction with the species composition of Task
II data. This statistical problem in the bigeye geographical distribution is a source of errors in
the choice and analysis of FAD moratoria. It is also a source of potential error in the Task 1
bigeye catches. Based on fine scale sampled catches, bigeye catches by the Ghanaian fleet could
be widely overestimated today because of its improper data processing. Our study makes the
recommendation that improved Task II statistics should be prepared for the EU&al PS and for
the Ghanaian fleet before the bigeye stock assessment
Les grands marquages de thons de la CTOI 2005-2009 : les principaux résultats préliminaires des marquages et quelques unes de leurs conséquences
Analyse des rendements des chalutiers ivoiriens. Définition d'un effort de pêche
A comparison between the yields obtained during 1968 and 1969 from the trawlers based at Abidjan harbour was carried out in various fishing areas. Seasonal fluctuations of abundance were first eliminated and then the regression between yield and motor power was calculated. The unit of fishing effort, one hour of fishing for a standard trawler of 400 BHP, was chosen for the fishing statistics of the Ivorian fleet
A framework for the standardisation of tropical tuna purse seine CPUE: application to the yellowfin tuna in the Indian Ocean
We revised the existing framework for tuna CPUE standardisation in light of the increasing literature that
advocates the use of mixed effects models to account for the characteristics of logbook data. We apply the
framework on yellowfin tuna (YFT) from the Indian Ocean, caught by the purse seine EU fleet (Spain and
France) from 1984 to 2015. We used a comprehensive list of candidate covariates, including non- conventional covariates, and run exploratory models to assess the contribution of each covariate. Due to the
large number of covariates, the lasso – least absolute shrinkage and selection operator- method was applied
for data mining and model selection purposes. The results are two standardised YFT CPUE time series for the
period 1984-2015, one for large fish caught in free-school related sets, and one for mainly juveniles caught in
floating object related sets. Issues on the usefulness of highly aggregated data (low resolution: annual and
fleet wide) is discussed along with the need for more detailed information on the use of dFADs, preferably at
the level of a fishing trip.Preprin
Pêche, biologie et dynamique du tassergal (Pomatomus saltator, Linnaeus, 1766) sur les côtes sénégalo-mauritaniennes
Using historical fisheries data to predict tuna distribution within the British Indian Ocean Territory marine protected area, and implications for its management
1. Recently, several large marine protected areas (MPAs) have been established globally and it is hoped that they will aid the recovery of populations of highly-mobile, large pelagic species. Understanding the distribution of these species within MPAs is key to delivering effective management but monitoring can be challenging over such vast areas of open ocean. 2. Historical fisheries data, collected prior to reserve establishment, can provide an insight into the past distributions of target species. We investigated the 10spatial and temporal distribution of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tuna catch using logbook data from the purse seine fishery in British Indian Ocean Territory (BIOT) from 1996 to 2010, before it was established as an MPA in April 2010. 3. Generalized additive models (GAMs) were used to predict tuna presence and relative abundance from fishing records in relation to temporal and environmental variables. Significant variables included sea salinity, temperature and water velocity. 4. Predictions from the models identified a distinct hotspot for large yellowfin tuna within the MPA, and areas of high predicted relative abundance of skipjack tuna. We recommend that these areas are used as focal points from which populations can be monitored and investigations into tuna residency time can occur, so that the effectiveness of the MPA in conserving highly-mobile pelagic fish can be determined
Generating informative trajectories by using bounds on the return of control policies
Abstract We propose new methods for guiding the generation of informative trajectories when solving discrete-time optimal control problems. These methods exploit recently published results that provide ways for computing bounds on the return of control policies from a set of trajectories. Keywords: reinforcement learning, optimal control, sampling strategies Introduction. Discrete-time optimal control problems arise in many fields such as finance, medicine, engineering as well as artificial intelligence. Whatever the techniques used for solving such problems, their performance is related to the amount of information available on the system dynamics and the reward function of the optimal control problem. In this paper, we consider settings in which information on the system dynamics must be inferred from trajectories and, furthermore, due to cost and time constraints, only a limited number of trajectories can be generated. We assume that a regularity structure -given in the form of Lipschitz continuity assumptions -exists on the system dynamics and the reward function. Under such assumptions, we exploit recently published methods for computing bounds on the return of control policies from a set of trajectorie
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