Evidence of a range expansion in sunfish from 47 years of coastal sightings

• Published in: Marine biology Vol. 169; no. 2; p. 20
• Main Authors: Lyashevska, Olga, Brophy, Deirdre, Wing, Steve, Johns, David G., Haberlin, Damien, Doyle, Thomas K.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2022; Springer; Springer Nature B.V
• Subjects: Abundance; Anthropogenic changes; Anthropogenic factors; Biomass; Biomedical and Life Sciences; Birds; Citizen scientists; Climate change; Colour; Commercial fishing; Correlation; Distribution; Environmental aspects; Fish; Fisheries; Fishing; Freshwater & Marine Ecology; Freshwater fishes; Influence; Isotherms; Life Sciences; Marine & Freshwater Sciences; Marine biology; Marine fishes; Marine invertebrates; Methods; Microbiology; Observatories; Oceanography; Original Paper; Overfishing; Phytoplankton; Plankton; Probability theory; Range extension; Research centers; Sea surface; Seabirds; Sunfishes; Tuna; Zoogeography; Zoology; Ireland; Dermochelys coriacea; Jellyfish; Muggiaea atlantica; Citizen science; Mola mola; Hurdle model
• ISSN: 0025-3162; 1432-1793
• DOI: 10.1007/s00227-021-04005-8

Almost nothing is known about the historical abundance of the ocean sunfish. Yet as an ecologically and functionally important taxa, understanding changes in abundance may be a useful indicator of how our seas are responding to anthropogenic changes including overfishing and climate change. Within this context, sightings from a coastal bird observatory (51.26 ∘ N, 9.30 ∘ W) over a 47 year period (from April to October 1971–2017) provided the first long-term index of sunfish abundance. Using a general linear mixed effect model with a hurdle to deal with imperfect detectability and to model trends, a higher probability of detecting sunfish was found in the 1990s and 2000s. Continuous Plankton Recorder (CPR) phytoplankton color indices and the annual mean position of the 13  ∘ C sea surface isotherm were significantly correlated with the probability of detecting sunfish. An increase in siphonophore abundance (as measured by the CPR) was also documented. However, this increase occurred 10–15 years after the sunfish increase and was not significantly correlated with sunfish abundance. Our results suggest that the observed increase in sunfish sightings is evidence of a range expansion because it was significantly correlated with the mean position of the 13 ∘ C isotherm which moved northwards by over 200 km. Furthermore, the observed increase in sunfish occured  10 years before sunfish sightings are documented in Icelandic and Norwegian waters, and was concurrent with well-known range expansions for other fish species during the 1990s. This study demonstrates how sustained citizen science projects can provide unique insights on the historical abundance of this enigmatic species.