Analysis of Long-Term Changes in a Mediterranean Marine Ecosystem Based on Fishery Landings

Abstract

In the Mediterranean Sea, structured and standardized monitoring programs of marine resources were set only in the last decades, so the analysis of changes in marine communities over longer time scale has to rely on other sources. In this work, we used seven decades (1945-2014) of disaggregated landings statistics for the Northern Adriatic Sea (Mediterranean) to infer changes in the ecosystem. Analysis of landings composition was enriched with the application of a suite of ecological indicators (e.g., trophodynamic indicators, such as the primary production required to sustain the catches-PPR; size-based indicators, such as the large species indicator-LSI; other indicators, such as the elasmobranchs-bony fish ratio-E/B ratio). Indicators were further compared with main ecosystem drivers, i.e., fishing capacity, nutrient loads and climate change. Species most vulnerable to fishing (i.e., elasmobranchs and large-sized species) dramatically declined at the beginning of the industrialization of fishery that occurred right afterwards World War II, as can be inferred by the negative drop of LSI and E/B ratio in the mid-1950s. However, until the mid-1980s landings and PPR increased due to improvements in fishing activities (e.g., the introduction of more efficient fishing gears) increasing fishing capacity, high productivity of the ecosystem. Overall, the effects of fishing were buffered by an increase in productivity in the period of high nutrient discharge (up to mid-1980s), while significant changes in fish community structure were already occurring. From the mid-1980s, a reduction in nutrient load caused a decline in productivity but the food-web structure was already modified and unable to support, or recover from, such unbalanced situation, resulting in the collapse of landings. This collapse is coherent with alternative stable states hypothesis, typical of complex real systems, that implies drastic interventions that go beyond fisheries management and include regulation of nutrient release for recovery. The work highlights that, despite poor capabilities to track species dynamics, landings and applied indicators might help to shed light on the long-term dynamics of marine communities, thus contributing to place current situation in an historical framework with potential for supporting management.

Local Ecological Knowledge Indicates Temporal Trends of Benthic Invertebrates Species of the Adriatic Sea

“…In 1980s, Italian Adriatic regions reached the maximum number of fishing vessels together with the complete development of highly damaging fisheries introduced in the 1960s (Froglia, 2000;AdriaMed, 2004;Romanelli et al, 2009). In the 2000s the total number of fishing vessels decreased (AdriaMed, 2004), however, new technologies such as GPS systems have been introduced, improving the exploitation of new fishing ground (Fortibuoni et al, 2017) and the total fishing pressure on Adriatic seabed bottoms is currently considered unsustainable. Because the LEK data we collected in our study to detect fishers' perceptions is mainly qualitative, our models did not detect clear patterns moving from coastal to offshore areas.…”

Recent Trends and Impacts of Fisheries Exploitation on Mediterranean Stocks and Ecosystems

“…The ecosystem change was so fast during the last 50 years to be directly witnessed in different Mediterranean areas by fishermen and vessel captains , highlighted from analysis of landing statistics (Fortibuoni et al, 2017), and documented in several studies (Lleonart, 1993;Abelló et al, 2002;Coll et al, 2006Coll et al, , 2007Libralato et al, 2008;Azzurro et al, 2011).…”

“…Pollution and marine litter are having strong attention because of the several indirect and direct impacts on both stocks and fisheries (Galgani, 2015). Nutrient loads from watershed have been regulated with important changes in the last decades resulting in direct effects on marine coastal area primary productivity and exploited resources (Caddy, 2000;Fortibuoni et al, 2017). Climatic global changes are also influencing Mediterranean marine communities by changing average temperature, productivity and water alkalinity (Lazzari et al, 2012(Lazzari et al, , 2014Cossarini et al, 2015) with potentially large effects on exploited stocks (Colloca et al, 2014).…”

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).…”