Climate change and fishing: a century of shifting distribution in North Sea cod

Abstract

Globally, spatial distributions of fish stocks are shifting but although the role of climate change in range shifts is increasingly appreciated, little remains known of the likely additional impact that high levels of fishing pressure might have on distribution. For North Sea cod, we show for the first time and in great spatial detail how the stock has shifted its distribution over the past 100 years. We digitized extensive historical fisheries data from paper charts in UK government archives and combined these with contemporary data to a time-series spanning 1913–2012 (excluding both World Wars). New analysis of old data revealed that the current distribution pattern of cod – mostly in the deeper, northern- and north-easternmost parts of the North Sea – is almost opposite to that during most of the Twentieth Century – mainly concentrated in the west, off England and Scotland. Statistical analysis revealed that the deepening, northward shift is likely attributable to warming; however, the eastward shift is best explained by fishing pressure, suggestive of significant depletion of the stock from its previous stronghold, off the coasts of England and Scotland. These spatial patterns were confirmed for the most recent 3½ decades by data from fisheries-independent surveys, which go back to the 1970s. Our results demonstrate the fundamental importance of both climate change and fishing pressure for our understanding of changing distributions of commercially exploited fish.

Responses of Marine Organisms to Climate Change across Oceans

“…Recent warming in the southern section has facilitated the southward expansion of flatfish species, previously excluded by cold winter temperatures, into southern coastal areas. Similarly, the distribution of North Sea cod, G. morhua, has shifted northeastward and deepened over 100 years (Engelhard et al, 2014). The northward shift is explained by warming and the eastward shift by fishing, through a serial depletion of cod from the western section of its historical distribution.…”

Environmental Impacts—Marine Ecosystems

“…There has been a remarkable westward jump in the plaice distribution since the late 1980s, apparently reflecting a collapse of the population in the east-central North Sea and increased abundance off Scotland (Engelhard et al 2011). A similar analysis of changes in North Sea cod since 1912 (Engelhard et al 2014) shows that their distribution shifted northward, but only since the late 1990s, and can be related to temperature. A major west to east shift in cod distribution from the early 1980s to 2000 can be related to fisheries-induced reduction in stock biomass rather than climate.…”

Land- und Forstwirtschaft, Fischerei

“…7.10 Anlandemengen in Tonnen der 10 wichtigsten Zielarten in der deutschen Fischerei im Jahr 2013. (BLE 2014) während der letzten 100 Jahre (Engelhard et al 2011(Engelhard et al , 2014 (Engelhard et al 2014).…”