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

Abstract

Marine communities have long been impacted by human activities, but the quantification of human‐driven changes often relies on recent data. This is because historical data on fish populations are lacking and are challenging to include in contemporary stock and ecological assessments. As a result, the impacts of early fishing pressure on marine communities are generally poorly documented worldwide. Marine communities of Southeast Australia have a relatively short history of exploitation compared with other temperate systems and were sampled before and after the onset of commercial fishing. As such, they provide a rare opportunity to identify historical baselines and to understand ecological changes after the onset of commercial exploitation. This study compares survey data collected around Tasmania, Southeast Australia, in 1909–1910 with data from the 1980s. The period considered precedes the establishment of a trawl fishery in Southeast Australia in 1915, of other important commercial fisheries in Tasmania, and of a fisheries data collection programme in 1984. Nominal catch rates are used to examine changes across all families of demersal fish recorded in catches and generalized linear models are used to estimate and compare standardized indices of abundance between the 1909–1910 and 1980s data for key commercial families. Results show significant, and thus far unreported, fishing‐induced changes in marine communities after the establishment of commercial fishing in the region. Changes mostly relate to shifts in catch composition and steep declines in the abundance of the main commercial families. This study illustrates a method for analysing low‐quality historical catch data and provides estimates of pre‐commercial fishing abundance that can be included in stock and ecological assessments. More broadly, this study demonstrates the significant role of early fishing in shaping marine communities and increases our understanding about general patterns of exploitation that have been difficult to identify with longer but less detailed fishing histories.

Changes in trophic structure of an exploited fish community at the centennial scale are linked to fisheries and climate forces

“…Accelerating anthropogenic stressors, such as climate change and fisheries exploitation, have driven extensive changes in the abundance 5 and distribution 6 of marine organisms. While these effects have altered community composition 7 , little is known about their long-term impacts on the trophodynamics of marine food webs in natural systems.…”

“…Examples from natural systems are rare but are essential if we are to understand the broader implications of natural processes and human activities for marine food webs 18 . For instance, overexploitation and ocean warming have had increasing influences on marine communities and ecosystem function over the last century 7 , 19 , 20 , with cumulative impacts observed across more than half of the global ocean 21 . In this context, long-term studies that incorporate archival samples to measure changes in trophic structure can provide important new insights into how the relatively recent history of human impacts have modified natural marine food webs 22 – 24 .…”

Exploring trade‐offs in mixed fisheries by integrating fleet dynamics into multispecies size‐spectrum models

“…The fleet dynamics component is based on gear types, fleet profitability and management regulations, and it allows fleets to compete over species. We parameterise and calibrate the model to represent the Australian Southern and Eastern Scalefish and Shark Fishery, which is a multi-sector, multispecies fishery that covers almost half of the Australian Fishing Zone and is one of Australia's most complex fisheries (Novaglio et al, 2018(Novaglio et al, , 2020. Using this model and the fishery, it represents as our case study, we evaluate a range of fleet competition scenarios and assess their performance using ecological and economic indicators.…”

300 years of change for native fish species in the upper Danube River Basin – historical flow alterations versus future climate change

“…Therefore, placing predicted future changes into a historical context can deliver useful information regarding the magnitude of change that species have already been exposed to, compared to what they would expect under future climate change scenarios. Such information would significantly increase the effectiveness of current conservation management efforts (Bonebrake et al, 2010;Novaglio et al, 2020;Pont et al, 2015).…”