In this month’s “In Depth”, we discuss how bottom trawling is navigating a transition in a Mediterranean subjected to intense socio-environmental pressures.
The western Mediterranean is today a space of ecological, political, and socioeconomic limits. In this sea —as ancient as it is shaped by human activity— bottom trawling, a key activity for the economy and identity of the coastal communities in Catalonia, finds itself pulled between the need to continue fishing and the evidence that ecosystems can no longer sustain past levels of exploitation. The data make this clear, and so do the experts working working daily on the issue.
“We are in a moment of accelerated transition,” summarizes ICM-CSIC researcher Marta Coll. “Pressures on the marine ecosystem have grown so much and so fast that we can no longer manage fisheries in isolation; they must be integrated as one component of a marine socioeconomic system embedded within an ecological system highly strained and changing.”
The list of pressures is long and well-known: decades of accumulated overfishing, constantly expanding maritime transport, intensive coastal uses, land-based pollution and, across all of this, climate change altering the distribution and productivity of many species. Together, these factors create a scenario in which the margin for error or inaction is narrowing. As Coll reminds us, “when the Marine Strategy Framework Directive evaluations show that many indicators fail to reach the minimum thresholds needed to achieve good environmental status, it means there is no buffer left: a bad decision has rapid and difficult-to-reverse consequences”.
The challenge of transforming trawling
In this context, bottom trawling is perhaps the fishing method under greatest tensions. By definition, dragging a net along the seabed implies significant physical and ecological impacts on benthic habitats. However, the debate is not as simple as banning or maintaining it, but about how to transform it.
“The question we are currently asking is what kind of trawling we want and can afford in a context of fragile ecosystems, and what incentives and tools we need to make this change possible,” explains ICM-CSIC researcher Miquel Ortega.
Since 2019, the European Union has promoted a Multiannual plan for demersal stocks in the western Mediterranean Sea with measures that, according to early indications, are beginning to deliver results: progressive reductions in fishing pressures, gear modifications to improve selectivity, new closure areas, and longer temporal cessation of fishing activities. These actions, Coll notes, “have been necessary, although they arrived late, when the marine ecosystem is already heavily degraded.” The stocks assessed —still very few compared to the total number of exploited species— show slight improvements compared to a decade ago; but these improvements must be interpreted cautiously. Biomass estimation models have significant limitations and high uncertainty, as experts remind us.
“Saying that some stocks are doing better is not the same as saying that the stocks or the ecosystem are in good condition; it means we are moving forward, but we are still far from the levels required to ensure an ecological system resilient to the growing pressures we impose on it and capable of adapting to climate change,” explains Coll.
The latest evaluations from the EU’s scientific council (STECF) confirm this fragility. Iconic species such as European hake (Merluccius merluccius) or Norway lobster (Nephrops norvegicus) remain at very low biomass levels, with high fishing mortality and little capacity for recovery. Regarding shrimps —a particularly sensitive resource in the northwestern Mediterranean— ICATMAR reports indicate that, according to most assessment methods applied, blue and red shrimp (Aristeus antennatus) is in worse condition than deep-water rose shrimp (Parapenaeus longirostris). For blue and red shrimp, the specie of greatest economic value, most models still consider biomass to be below established targets —though improving— and fishing pressure above targets —though decreasing.
They also warn of increases in discards of small shrimps to avoid exceeding legal maximum capture limits —as fishers concentrate commercial landings on larger, higher-value individuals and discard the small ones dead to avoid counting them— a factor that must be considered in the future to prevent distorting the real perception of abundance. There is also a perception in fishing harbours that IUU sales of this valuable species may be increasing again. Added to these changes in fishing practices there is a shift in the distribution of fishing effort: some larger vessels, traditionally working in deeper areas, have increased their activity in coastal grounds due to shrimp catch limits, adding pressure to nearshore ecosystems already facing heavy overexploitation.
An uncertain future
The sector faces major socioeconomic challenges as well: an ageing fleet, severe difficulties attracting and retaining workers, and volatile operational costs linked to fluctuating fuel prices. The overall viability of the activity remains fragile, heavily dependent on public aid and subsidies, and confronted with market challenges such as increasing competition and shifting consumer habits that often reduce demand for trawl-caught products.
Yet not everything is negative. The slight recovery of some stocks and the increase in selling prices in recent years —combined with lower operational costs thanks to fewer days at sea and lower fuel prices— have led to a substantial rise in profits for much of the Catalan trawler fleet over the last three years. “The ecosystem is changing, and so is the socioeconomic context of consumption and commercialization. That’s why it is essential to commit decisively to a transition that integrates all factors and assumes that the fleet will continue to change —maintaining the status quo is not an option,” insists Ortega.
The transition proposed by researchers includes consolidating more selective practices; improving commercialization; adopting an ecosystem-based approach that also integrates social and territorial dimensions; and establishing clear planning with coherent long-term objectives agreed upon collectively to avoid improvisation every time a species reaches a critical state, along with deeper dialogue between scientists, administrators and the fishing sector.
The conclusion —if one can be drawn from such a complex situation— is that the future of Mediterranean trawling plays out on a narrow, but not non-existent, path. Current measures, despite implementation difficulties, have opened a window of opportunity, but it is short and will require political courage and collective co-responsibility to seize it and keep progressing.
“The Mediterranean has always been a sea of compromises. The challenge now is to build a new compromise: one that places ecosystem health at the centre and sets clear socio-economic objectives consistent with existing ecological limits —because everything else depends on that”, conclude Coll and Ortega.