Migration and Asylum Data for Policy-making in the European Union – The problem with numbers. CEPS Liberty and Security in Europe No. 89/March 2016

Among many other problems, the migration, humanitarian and policy crises in the European Union in 2015 and early 2016 have highlighted a pressing need for reliable, timely and comparable statistical data on migration, asylum and arrivals at national borders. In this fast-moving policy field, data production and the timeliness of dissemination have seen some improvements but the sources of data remain largely unchanged at national level. In this paper the author examines the reasons for some of the problems with the data for policy and for public discussion, and makes a set of recommendations that call for a complete and updated inventory of data sources and for an evaluation of the quality of data used for policy-making.

Compilation of North Atlantic albacore tuna (Thunnus alalunga) fork length frequencies in 5 centimeter intervals from catches in the North Atlantic for the period 1956-2010

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.