Thumbnail Image

Assessment of depredation level in Reunion Island pelagic longline fishery based on information from self-reporting data sampling programme

Year of publication 2013

Product type Meeting

Edition 1

Synopsis (short abstract) Depredation attracts broad intertiol attention during recent decades with worldwide expansion of fishing by passive gears, in particular pelagic and bottom longlines. Presumed steady increase of depredation level from the early years of fisheries to present (IOTC, 2000a, Donoghue et al., 2003, Gilman et al., 2007) and economic losses associated with this type of interaction (IOTC, 1999, 2000a, Bargain, 2000, 2001; Nishida, Tanio, 2001, Rabearisoa, 2012) were major concerns. Depredation is usuall y defined as “the partial or complete removal of hooked fish or bait from fishing gear...” by predators such as cetaceans, sharks, bone fish, birds, squids, crustaceans and others” distinguishing it from predation, i.e. “the taking of free swimming fish (or other organisms)...” (Donoghue et al., 2003; Gilman et al., 2006, 2007). Depredation mostly occur in statiory (passive) gears like pelagic and bottom longlines (Kock et al., 1996; Gilman et al., 2006, 2008), gillnets (Read et al., 2003), trap s, line fisheries (de Stephanis, 2004; Navarro, Bearzi, 2007) and within aquaculture facilities (Stickley et al., 1992; Coon, 1996; Glahn et al., 1999; Fenech et al., 2004; Kloskowski, 2005). However highly mobile fisheries like trolling, trawl and purse seine are also sometimes subject to depredation (often mixed with scavenging) by marine mammals (Zollett, Read, 2006, Zahri et al., 2004), squids (Olson et al., 2006), birds (Baker et al., 2007) or sharks (our unpublished data). Longline fishing operations suffered probably the most from depredation due to its worldwide distribution, statiory ture, long exposure (hours) in the environment, easy access to animal caught and gear fragility. Possible altertion of predators behaviour resulted from interactions with fishing gears was also suggested based on fact of depredation itself and different reaction to fishing gear among populations of the same species (Matkin et al., 2007). If alteration of predators? behaviour is really take place, potential wide impact on ecosystem scale might be envisaged. Depredation occurrence and respective losses of catch are usually not reported in the fisheries statistics and are a source of „cryptic mortality? that is not accounted for in current stock assessment studies, therefore affecting directly fisheries magement decisions and practice (Gilman et al., 2007, Romanov et al., 2007). Economic losses due to catch and gear damage have brought serious concerns to fishermen (Yano, Dahlheim, 1994; Ni shida, Tanio, 2001; Donoghue et al., 2003; Rabearisoa, 2012) while harm to marine megafau either through interactions with fishing gears or with fishermen who attempts to protect their catch (Gulland, 1986; Read, 2008) rises conservation issues. There is an obvious and urgent need for close monitoring of the depredation phenomenon, its quantification, incorporation into the fisheries magement schemes and development of mitigation measures. Here we report prelimiry results of depredation affectin g the local longline fishery operated from Reunion Island, basing on information from self-reporting data collection programme.

Statutory body / Meeting title Indian Ocean Tuna Commission (IOTC)

Meeting symbol IOTC-2013-WPEB09-47

Meeting Session Number 9

Language English

Also available in:
No results found.

Related items

Showing items related by metadata.

  • Thumbnail Image
  • Thumbnail Image
    Meeting
    Commercial catch and discards of pelagic longline fishery of Reunion Island based on the self-reporting data collection program 2013
    Also available in:
    No results found.
    Pelagic longline fishery activities of Reunion Island are monitored since 2011 by the self-reporting data collection program (SRP) that covered 12% of the total fishing effort in 2011-2012. Fishermen report in SRP various informations on fishing locations, gear used, catch, discards and depredation. We used these data to assess the levels and distribution of commercial catch and discards between mid-2011 and mid-2013. We found that the catch per unit of effort (CPUE) of swordfish (target species ) has decreased since 2011 as long as the overall profitability of this fishery including other commercial species and taxa: yellowfin tu, bigeye tu, albacore tu, dolphinfish and billfish. Discards were mostly blue sharks (38%), pelagic stingrays (24%) and a generic group of very long fish usually called snooks by fishermen (20%). In this context of overall decrease of fishery profitability, fishing on the east coast of Madagascar between July and September still remains a profitable strategy wh ile byctach rate of discards is reasobly low. Albacore tu season occurring the last quarter of the year also remains profitable with high albacore CPUE levels near Reunion Island and below average rate of discarded bycatch.
  • Thumbnail Image
    Meeting
    Self-reporting data collection project for the pelagic longline fishery based in La Reunion 2013
    Also available in:
    No results found.
    Overexploitation of target and bycatch species in marine capture fisheries is the most widespread and direct driver of degradation of marine communities and loss of global marine biodiversity. Logbook data in general covered only the part of the catch landed to be commercialized. Observer programs can be difficult to implement depending on the size of fishing boats and present several constraints leading to inferences biases. In this context, IRD with the cooperation of the CAP RUN launched in 2 011, a self-reporting of exhaustive catch and effort data for the pelagic longline fishery based in Reunion Island. The aim of this project is to increase the coverage level of the fishing activity of all longliners of the fleet in terms of fishing effort and spatial distribution. The project is undertaken with the fincial support of the “Data Collection Framework” program of the European Union. It is based on fincial motivations of collaborative fishermen. The selection of data to be collected corresponds to a compromise between data reported by observers, fisher?s knowledge and availability for data reporting. Information collected concerns the fishing activity, commercialized catch, discards and interactions between the gear and pelagic resources. In 2011 and 2012, 127 and 398 fishing operations were self-reported. The interest of this kind of project is discussed.
Show more

Users also downloaded

Showing related downloaded files

No results found.