Fish and Fisheries. 2018;1–13. wileyonlinelibrary.com/journal/faf | 1 © 2018 John Wiley & Sons Ltd Received: 4 December 2017 | Revised: 11 March 2018 | Accepted: 8 May 2018 DOI: 10.1111/faf.12298 ORIGINAL ARTICLE Larval abundance across the European eel spawning area: An analysis of recent and historic data Håkan Westerberg 1 | Michael J. Miller 2 | Klaus Wysujack 3 | Lasse Marohn 3 | Marko Freese 3 | Jan-Dag Pohlmann 3 | Shun Watanabe 4 | Katsumi Tsukamoto 2 | Reinhold Hanel 3 1 Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences, Drottningholm, Sweden 2 Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Fujisawa-shi, Kanagawa, Japan 3 Thünen-Institute of Fisheries Ecology, Hamburg, Germany 4 Department of Fisheries, Faculty of Agriculture, Kindai University, Nara, Japan Correspondence Håkan Westerberg, Institute of Freshwater Research, Stångholmsvägen 2, SE-178 93, Drottningholm, Sweden. Email: hakan.westerberg@slu.se Funding information German Federal Ministry of Food and Agriculture; Ministry of Education, Culture, Sports, Science and Technology of Japan, Grant/Award Number: 26-252030 Abstract The abundance and distribution of leptocephalus larvae of the European eel ( Anguilla anguilla, Anguillidae) were examined using ten historic and recent Sargasso Sea expe- ditions that were selected on the basis of having the largest number of sampling sta- tions and highest catches. The surveys cover the period 1920–2014. Station data were recalculated to the same unit of larval density per unit area, and the irregular station positions were transformed to a regular spatial grid to allow calculation of comparable measures of abundance of the youngest (0+) leptocephalus cohort. The result is that the mean and maximum densities of 0+ leptocephali after 2007 on aver- age have decreased by 70%–80% from the densities during the period before the drastic decrease in glass eel recruitment, which started in the 1980s. This is of the same magnitude as the change in spawning stock, if the total continental commercial landings are used as a proxy. In the same period, the glass eel recruitment in Europe has decreased by more than 95%. The conclusion is that a major cause for the recruit- ment decrease may be an increased leptocephalus mortality during the oceanic phase or a large geographic shift in glass eel arrival. Combining the survey data, the spatial distribution of 0+ leptocephali was concentrated south of the northernmost front in the Subtropical Convergence Zone, but high densities were also found far south of the front in the western part of the distribution area and leptocephali were present also north of the average frontal position. KEYWORDS Anguillid eels, larval distribution, leptocephalus, oceanic environment, population decline, recruitment 1 | INTRODUCTION The spawning area of the European eel, Anguilla anguilla, was discov- ered about a century ago by the Danish scientist Johannes Schmidt who revealed that the only place small larvae, called leptocephali, could be collected was in the southern Sargasso Sea (Schmidt, 1923). This was astonishing at the time and even today because it meant that the reproductive stage silver eels must migrate many thousands of kilometers to reach their distant oceanic spawning area (Righton et al., 2012). Schmidt’s sampling for leptocephali in the Sargasso Sea began last century after no small leptocephali of A. anguilla were collected in the Mediterranean Sea or offshore of western Europe (Schmidt, 1906, 1909, 1912a,b). His effort to find the spawning area of A. an- guilla moved offshore in the North Atlantic Ocean after 40–60-mm leptocephali of that species were collected in the central Atlantic