Arni Magnusson

Timeline

1. 1998–2002

   Degrees in Iceland and Seattle

   He earns a B.S. at the University of Iceland in 1998, serves as a teaching assistant in Fisheries Biology I, and works summer jobs at the Icelandic Marine Research Institute's Modelling Division under Gunnar Stefansson. At the University of Washington, he completes an M.S. in 2002 under Ray Hilborn as a Fulbright grantee and serves as a teaching assistant in Fish 458 (Fisheries Stock Assessment).

2. 2016

   A Washington doctorate

   Supervised by Ray Hilborn and Andre Punt, he completes a Ph.D. at the University of Washington in 2016. During his time at Washington, he is also a lecturer in Fish 507 (Numerical Computing).

3. 2016–2018

   Building TAF at ICES

   In July 2016, after stock assessment work in New Zealand and Iceland, he joins the ICES Secretariat as a professional officer to design and implement, with Colin Millar, a system that runs and stores all the stock assessments that go through ICES. In May 2018, he guides the Working Group on the Biology and Assessment of Deep-sea Fisheries Resources (WGDEEP) through the new Transparent Assessment Framework (TAF), and together they run the assessment of the Icelandic ling stock.

4. 2017

   The glmmTMB package

   In 2017, as a scientist at the International Council for the Exploration of the Sea (ICES), he coauthors the R Journal paper that introduces glmmTMB, a package for zero-inflated generalized linear mixed models. The models are fitted using maximum likelihood estimation via TMB (Template Model Builder), which calculates gradients by automatic differentiation, and the paper reports that glmmTMB is faster than glmmADMB, MCMCglmm and brms and more flexible than INLA and mgcv. He also serves on the ADMB Core Team, which maintains the source code of AD Model Builder.

5. January 2021

   A Nature Sustainability study

   In January 2021, he is among the coauthors, with Ray Hilborn and others, of "Identifying management actions that promote sustainable fisheries" in Nature Sustainability. The study compiles detailed management histories for 288 assessed fisheries from around the world and uses hierarchical time-series analyses to estimate the effects of management interventions on stock status.

6. April 2026

   The fishstat R package

   In April 2026, he publishes the fishstat R package on CRAN as author and maintainer with coauthor Rishi Sharma, providing FAO global fishery and aquaculture production data.

7. As of October 2026

   Tuna assessments at SPC

   Following earlier work at Hafro and at FAO as a senior biostatistician creating STAR, he is a Senior Fisheries Scientist at SPC, where his work focuses on tuna assessments and the management of scientific data and workflows for the Western and Central Pacific Ocean. With coauthors Colin Millar and Iago Mosqueira, he authors and maintains the TAF R package, whose version 4.3.1 is published in September 2025.