New publication about seabird bycatch in the artisanal demersal longliners of the Balearic Sea (northwestern Mediterranean)

No Comments

cortes_yel2The mortality caused by demersal longliners operating in the Balearic Sea is high and may be jeopardizing the viability of the shearwater populations. Therefore, the identification and implementation of mitigation measures is urgently required.

This is the main conclusion reached in the work we recently published about seabird interactions with the artisanal demersal longliners of the northwestern Mediterranean and the resulting bycatch rates. This study constitutes part of my PhD work conducted in the University of Barcelona and directed by the researcher Jacob González-Solís. In addition, we also relied on the collaboration of Pep Arcos of SEO/Birdlife.

Cortés V., Arcos JM., González-Solís J. 2017. Seabirds and demersal longliners in the northwestern Mediterranean: factors driving their interactions and bycatch rates. MEPS 565: 1–16.

In this paper, we provide information about the characteristics of the demersal longline fishery operating in the area, the main factors influencing the seabird interactions with vessels (using the attacks on bait as a proxy of the bycatch risk) and an estimation of the bycatch mortality caused by the fishery. This information is derived from on-board observations carried out throughout the entire the Balearic Sea (2011-2015) and the seabird catches which were reported voluntarily by fishermen when observers were not in the boats.becares_cona

We found that there is a higher risk of bycatch during spring, which coincides with the breeding season of seabirds, and also when fishermen set their longlines during sunrise. Other important factors were the bait type, wind conditions, gear configuration (distance between the weights that are attached to the lines) and proximity to the breeding colonies. The birds which are most vulnerable to bycatch in the Balearic Sea were the 3 Mediterranean species of shearwaters: Scopoli’s, Balearic and Yelkouan shearwater (Calonectris diomedea, Puffinus mauretanicus and P.yelkouan), often involving multi-catch events of several dozens of birds due to their flocking behaviour and deep-diving capabilities. We estimated an overall average bycatch rate of 0.58 birds per 1000 hooks, which would imply a conservative estimate ranging from 274 to 2,198 seabirds killed annually by demersal longliners in the area. This high mortality found in the Balearic Sea would be unsustainable and therefore of concern, especially because it is affecting threatened species that are suffering a severe decline of their already reduced populations, like the Critically Endangered Balearic shearwater.

Photo: Vero Cortés

We hope this work serves to draw attention to the high impact that the longline fisheries are having on local shearwater populations, and that it prompts urgent actions to reduce these incidental catches in the Balearic Sea. The Seabird Task Force is precisely using this previous experience to test and come out with the best solutions to minimize the problem. Indeed, currently we are testing the feasibility of using the vertical lines typically employed by Chilean fishermen (see last month’s post). This configuration increases the sink rate of the baited hooks and, hence, reduce the seabird access to the bait and the chance of the birds being hooked (Working together to make longline gear safe for seabirds in the Spanish Mediterranean).

My PhD work received the support of the Fundación Biodiversidad, EC LIFE+ Project INDEMARES, and a large number of fishermen, students and collaborators, as well as SEO/Birdlife.


Working together to make longline gear safe for seabirds in the Spanish Mediterranean

1 Comment

Working together with fishermen is essential for finding suitable solutions to reduce seabird bycatch. Their specialist knowledge about how their gear works and how to effectively catch their target species is helping us to design the most appropriate bycatch reduction methods without affecting their valuable catches. Hence, the main purpose of our demersal longline work for the next months is to encourage fishermen to cooperate and to enlist their direct involvement in finding solutions.

Our first challenge is testing the feasibility of a fishing gear configuration that is commonly used by artisanal fishers in Chile to target Austral hake (Merluccius australis). It has been demonstrated that this fishing gear has less impact on seabirds, as its rapid sink rate limits the seabird’s access to baited hooks. This is a key feature to reduce the catches of the diving species which can reach a depth of several meters, such as the shearwaters. Through the support of the ACAP Secondment Programme, I was in Chile for two months with the aim of understanding “in situ” how the Chilean gear works, its main components and characteristics. The experience I gained is now being used to tackle bycatch mitigation in the local demersal longline fishery in Catalonia- essentially adapting the Chilean gear to Spanish boats.

The gear is composed of a number of vertical lines o “espineles” distributed along a horizontal line (Figure 1). Each vertical line contains several hooks located at different depths and, at the end, there is a large weight that pulls the hooks down very quickly, reducing the time that bait is available to seabirds and therefore their risk of being bycaught.

Figure 1. Longline types used by Austral hake artisanal fleet. Moreno et al 2006


Antonio, a longline fisherman from Llançà (Northern Catalonia), is  working with our team on the process of adapting the Chilean gear to the local boats. His long experience and contribution are crucial to building the gear correctly, to finding the most effective variations and to assessing its feasibility.

Antonio is working with our team to test the feasibility of the vertical lines. Photo: Vero Cortés

In these last weeks, we have gone to sea with Antonio to make the first tests with the new gear. These initial trips served to learn how the gear works and to reveal possible problems or what we should improve. We also collected data on how fast the baited hooks are sinking, and our preliminary outcomes showed that they sink at around 0.8 m/s in first 10m depth, this being far greater than the sink rate recommended to avoid seabird catches (0.3 m/s). Regarding the commercial fish catches, unfortunately we haven’t caught any individuals of the target species yet, although at this moment the number of settings achieved is still insufficient to make a proper assessment of these results. We will post again soon to let you know how our trials get on!


Moreno, C. A., Arata, J. A., Rubilar, P., Hucke-Gaete, R., & Robertson, G. (2006). Artisanal longline fisheries in Southern Chile: Lessons to be learned to avoid incidental seabird mortality. Biological Conservation, 127(1), 27–36.


First bycatch data collected by Seabird Task Force observers in Spain


According to previous information, May and June is the most dangerous time of the year for seabird bycatch in the Western Mediterranean and observer effort has been intensified. The bycatch of the 3 Cory’s shearwaters (Calonectris diomedea) has occurred during three monitored fishing operations. Cory’s shearwater was the main species attending at demersal long-liners during the line setting and hauling.

Cory's shearwater Calonectris diomedea accidentaly captured on a pelagic long-liner
Cory’s shearwater Calonectris diomedea accidentaly captured on a demersal long-liner. Photo: Albert Cama

The analyses of the corpses indicated that some dead birds could be active breeders, showing breeding patch. The internal analysis of one bird indicated that it was an adult female.

See breeding patch on a Cory's shearwater Calonectris diomedea
See breeding patch on a Cory’s shearwater Calonectris diomedea Photo: Albert Cama

In addition to the data collected by SEO/BirdLife observers, fishermen reported the bycatch of other seabirds during the last weeks, including another Cory’s shearwater, 2 Atlantic gannets (Morus bassanus) and up to 40 unidentified shearwaters, including a massive event of 20-30 birds. We should mention that the skipper aborted the line setting due to the big amount of seabirds attacking to bait. Two Mediterranean European shags (Phalacrocorax aristotelis desmarestii) were accidentaly captured on cuttlefish pots. Additionally, 2 Cory’s shearwaters, 2 Yelkouan shearwaters (Puffinus yelkouan) and 5 Balearic shearwaters (Puffinus mauretanicus) were found death in one beach in Tarragona, they did not showed the presence of hooks, but some injuries near the mouth, indicating Long-line bycatch.

We wish to thank the collaboration of fishermen by allowing observers on board and reporting data.

Cory's shearwater Calonectris diomedea eating discarded fish from a demersal Long-liner
Cory’s shearwater Calonectris diomedea eating discarded fish. This has been the most abbundant species attending demersal long-liners. Photo: Albert Cama

International workshop on Marine Important Bird Areas in the Mediterranean

1 Comment


An international workshop on Marine Important Bird Areas in Malta and the Mediterranean will be held between the 23rd – 25th November 2015 by the LIFE+ Malta Seabird Project and BirdLife International. The workshop will be a key opportunity to gather knowledge and experience on protecting seabirds across national boundaries and international waters of the Mediterranean as well as set the way forward for international collaborations in protecting our common seabird heritage. (more…)


Long-liners in the Catalan coast

No Comments

The Spanish team is focused in the Catalan harbours, where different kinds of long-liners operate. The main target of this project is the demersal long-liner fleet, but other boats using artisanal or pelagic long-lines also operate in the area. In fact, in the harbours where we have started our work -Llançà, Roses and Vilanova i la Geltrú- we can find boats using the different long-line types. In this blog post, we will quickly point out the differences between these similar fishing gears.As we know, long-lines are composed by a main line with several hooks attacked to it, but this general configuration can be set in a plethora of different variations which can be grouped in 3 main classes:

Pelagic long-lines: This fishing gear requires floats to keep the gear close to the sea surface. In the Catalan coast, the fishermen generally target large pelagic predators like swordfish or tunas. They set a few thousand large hooks separated by a distance that can exceed 30 m. In this project we do not pay attention to this fishing method, since the Spanish Oceanographic Institute has an on-going long-term project with on-board observers on these fishing boats.

Example of pelagic longline configuration.  Bycatch mitigation factsheet 8. BirdLife
Example of pelagic longline configuration. Bycatch mitigation factsheet 8. BirdLife
Pelagic longliner at Torredembarra harbour. Photo: Matxalen Pauly
Pelagic longliner at Torredembarra harbour. Photo: Matxalen Pauly

Demersal long-lines: Targeting bottom species, like hake or breams, the fishing gear is sunk by the use of weights, which are combined with floats to keep the gear on the right placement for the target species. They set a similar amount of smaller  hooks, which are spaced very few meters.

Longline box with the hooks, some with the bait. Photo: Pau Calero
Longline box with the hooks, some with the bait. Photo: Pau Calero
Demersal long-liner off central Catalonia
Demersal long-liner off central Catalonia

Artisanal long-lines: The main characteristic of this fishing gear is its small scale. This fishing gear can be very similar to demersal long-liners, but they use a few hundreds of hooks which are set in relatively shallow waters close to the coast line.

Artisanal long-liner at Roses harbour
Artisanal long-liner at Roses harbour

The Seabid Task Force starts on-board surveys on Spanish long-liners to assess seabird by catch.

No Comments

After some weeks of continuous northern winds, the 2nd and 3rd of March the first STF surveys on-board of demersal long-liners in Spain were conducted. One observer of SEO/BirdLife shipped on a demersal long-liner based in Llançà, one of northernmost Catalan harbours next to the Spanish-French border. The main target of the fishing boat was the Blackspot seabream Pagellus bogaraveo. These first surveys were worth improving the methodology, getting familiar with it and collecting the first data. We characterised the fishing gear configuration and effort and observed no seabird bycatch. We also enjoyed of a very tasty on-board meal, which was worth recovering strength and knowing the fishermen from a personal point of view.

Black legged kitty-wake (Rissa tridactyla) following the vessel during the operations
Black legged kitty-wake Rissa tridactyla following the vessel during the operations

Only very few Yellow-legged gulls Larus michahellis, Mediterranen gulls L. melanocephalus and Kittywakes Rissa tridactyla followed the vessel during the operations. Seabirds ate discarded baits and one kittiwake stole one bait when setting but was not hooked. The shearwaters (only Mediterranean, Puffinus yelkouan) were very scarce during the operations, and most individuals were observed in coastal waters when returning to port.

During the following weeks we will keep contacting long-liner skippers and continue with on-board observations.

Only fishes were fished
Only fishes were fished

New population estimates for the Balearic shearwater: Should we let down our guard?

No Comments

The Seabird Task Force is working to quantify and reduce bycatch of Balearic Shearwaters. Read Pep Arcos’ (SEO/BirdLife) blog about the critically endangered population, the trends & threats.

European Seabirds Blog


Recently the media and social networks have echoed good news for our most endangered bird species, the Balearic shearwater Puffinus mauretanicus. Indeed, a study published this year in the scientific journal Bird Conservation International points to a global population of about 25,000 birds, roughly doubling the previous estimates. The study is based on data from the Migres Programme, and consists on the census of Balearic shearwaters crossing the Strait of Gibraltar in their outward movement towards the Atlantic, after breeding. The information is consistent with another study of SEO/BirdLife, which followed a different approach (the census of birds in waters off the Iberian Mediterranean in late autumn, when the birds are back from the Atlantic. In fact, both approaches had been already published together, although the new paper provides more detail on the methodology used in the Strait of Gibraltar. The issue is also considered in…

View original post 1,122 more words


New Seabird Task Force to address bycatch in Europe: the Mediterranean point of view

1 Comment

915_1b_MARCA WEB


[Disponible en español]

BirdLife International is extending its Albatros Task Force, the initiative to reduce seabird bycatch in collaboration with fishermen, to Europe. Here, the so called Seabird Task Force starts at two bycatch hotspots, Lithuania and the Spanish Mediterranean. Reasons to prioritise this latter area deserve some further explanation.

Spain has a wide diversity of seabirds, with over 40 regular species, more than 20 of them breeding, spread across three distinct geographical regions: the Macaronesia, the European Atlantic and the Mediterranean. Of these, the Mediterranean hosts smaller seabird numbers, but a relatively high diversity of species, many of them of conservation concern precisely due to their tiny populations, as well as restricted distribution ranges. Moreover, the Mediterranean region is highly populated and therefore supports high human pressure, which affects seabirds in several ways: coastal development, introduced predators, pollution, fisheries overexploitation, etc. Among these, bycatch appears to be one of the most serious threats for some species.


Lithuania, Spain

Seabird Task Force in Europe established

1 Comment

The European Seabird Task Force is BirdLife’s new team of seabird bycatch experts. We are working with fishermen across Europe to tackle seabird bycatch.

The establishment of the Seabird Task Force means that BirdLife International and our Partners can actively contribute to the understanding of seabird bycatch within Europe and begin to develop and adapt solutions to this problem with fishermen across the region. The Seabird Task Force is the European incarnation of the successful ‘Albatross Task Force’, a team which has been working collaboratively with fishermen to tackle seabird bycatch in southern Africa and South America. Around the world, our approach is simple and all about collaboration- we work with local fishermen to understand the seabird bycatch problem and develop solutions together. This approach builds mutual respect between the team and the fishermen, and allows an effective collaboration to take place to solve a shared environmental and economic problem. (more…)