A centurial development of the North Sea fish megafauna as reflected by the historical Swedish longlining fisheries

Abstract

Historically, to compensate for declining catches, fishers have usually shifted from species characterized by high catch rate onto less easily caught species or have moved into new fishing grounds. Such shifts are poorly documented for areas with a long history of exploitation (i.e. North Sea) as they occurred long time before the start of the regular assessments of the marine resources. The Swedish longline fisheries in the Kattegat-Skagerrak and North Sea have a long history that spans over several centuries. These fisheries have historically targeted large demersal predator fish as ling (Molva molva), cod (Gadus morhua), Atlantic halibut (Hippoglossus hippoglossus) and skates (mainly Dipturus spp.). In this study, data from the Swedish longline fisheries from 1859 to 1960 have been collated. The data show that the geographical expansion of the fishery was extensive. At the turn of the 20th century, offshore longlining became concentrated north and west of the Shetlands and Hebrides, and after the WWII, the fishery expanded to Iceland and Rockall. In the offshore fishery, CPUE for the main target species, ling, remained stable, whereas for the other species, with the exception of tusk (Brosme brosme), CPUE showed a dramatic decline over time. In contrast, in the coastal longlining fishery, severe declines were revealed for all major target species except cod. We argue that the constant search for new fishing grounds in the Northeast Atlantic reflects a dwindling resource, where the fishermen kept the catch rates of ling high by travelling to more and more distant fishing grounds.

Identifying historical baseline at the onset of exploitation to improve understanding of fishing impacts

“…Most studies on historical ecology thus far have focused on communities of Europe or North America, where the fishing histories are generally longer and pre‐fishing data are challenging to find (e.g. Cardinale et al, ; Ferretti et al, ; Fortibuoni et al, ; Sáenz–Arroyo, Roberts, Torre & Cariño‐Olvera, ; Sáenz‐Arroyo, Roberts, Torre, Cariño‐Olvera, & Hawkins, ; Jackson et al, ; Thurstan et al, ). Hence, this study embraces a rare and timely opportunity by estimating the magnitude of ecological changes after the onset of commercial fishing in temperate fish communities of the Southern Hemisphere, which has received relatively little consideration to date (but see Alleway and Connell, () and Klaer (2010), for exceptions).…”

“…Most studies on historical ecology thus far have focused on communities of Europe or North America, where the fishing histories are generally longer and pre-fishing data are challenging to find (e.g. Cardinale et al, 2014;Ferretti et al, 2010;Fortibuoni et al, 2017;Sáenz-Arroyo, Roberts, Torre & Cariño-Olvera, 2005; Sáenz-Arroyo, Roberts, Torre, Cariño-Olvera, & Hawkins, 2006;Jackson et al, 2011;Thurstan et al, 2010).…”

“…In Southeast Australia commercial fishing developed relatively recently, often after the beginning of scientific investigations (Novaglio et al, 2018), as opposed to the situation in most other temperate systems (e.g. the Mediterranean, and in the Black and North seas; Cardinale et al, 2014;Fortibuoni, Libralato, Raicevich, Giovanardi, & Solidoro, 2010;Fortibuoni et al, 2017;Holm, Marboe, Poulsen, & Mackenzie, 2014;Thurstan, Brockington, & Roberts, 2010;Thurstan, Hawkins, & Roberts, 2014). This rare set of circumstances enables investigations that include data collected at the early stage of exploitation, and thus allows for an improved understanding of the role of fishing in shaping marine communities (Ermgassen et al, 2012).…”

Decline and diversity in Swedish seas: Environmental narratives in marine history, science and policy

“…Swedish fishermen who fished in offshore waters with longlines for large sized cod, ling (Molva molva) and other species in the Skagerrak and Kattegat were confronted at an early stage with falling catches. Lowering of the biomass level, especially the disappearance of big fish, forced artisanal Swedish fishers to explore new fishing grounds as their low-productive fishery became economically unsustainable already in the 1860s, unless the landings per unit effort was exceptionally high (Cardinale et al 2014). As the longliners left the Kattegat and Skagerrak for outlying areas, demersal trawling and other active forms of fishing were introduced on the Swedish west coast at the beginning of the twentieth century.…”

Fishery Development and Exploitation in South East Australia

“…Although our work considers the South East Australian region, it can also provide insight in understanding general patterns and consequences of exploitation that may be pertinent to other regions. This is because the history of commercial fishing in South East Australia is shorter than in many other temperate systems (e.g., Mediterranean, Black, and North Seas;Cardinale et al, 2014;Holm et al, 2014) and can be documented from end to end, and thus used to fill in information gaps occurring in marine systems with a longer history of exploitation.…”