Swordfish

Swordfish in the Indian Ocean were last assessed in 2017.  Several models including, Stock Synthesis 3, ASPIC, SCAA and BSP were used. The Stock Synthesis 3 model was determined to most likely represent the current status of swordfish in the Indian Ocean.  This model is spatially disaggregated, sex explicit and age structured. Information from 12 seperate fisheries was used in the assessment. The model included information on catches, discards, catch per unit effort from some longline fisheries, and size/age trends from 2950 through to 2015. A grid approach was used to quantify uncertainties in the model. The assessment treats swordfish as a single stock. In previous assessments information for swordfish from the southwest Indian Ocean was presented seperately but this is no longer done (IOTC 2017). 

The 2017 assessment indicated recent catches are at maximum sustainable yield (MSY) levels. The Scientific Committee's management advice is that catches should not be increased beyond MSY levels (31,590 t) (IOTC 2017)

Reference points for Swordfish in the Indian Ocean Tuna commission Area (IOTC 2017). 

2016 catch estimate: 31,407 tonnes
Average Catches (2012-2016): 31,142 tonnes
MSY: 31,590 (26,300-45,500) tonnes
SB₂₀₁₅/SB_MSY : 1.50 (1.05-2.45)
F₂₀₁₅/F_MSY : 0.76 (0.41-1.04)
SB₂₀₁₅/SB₀ : 0.31 (0.26-0.43)

Swordfish in the Indian Ocean are not overfished and overfishing is not occurring (IOTC 2017)

The current biomass of swordfish has been reduced to around 31% of virgin levels and is well above levels needed to produce the maximum sustainable yield.  There is a very low risk of the population becoming overfished over the next decade. Fishing mortality rates for swordfish in the Indian Ocean are well below levels needed to produce the maximum sustainable yield.  Recent catches of swordfish have been right around maximum sustainable yield levels (IOTC 2017).

There is one overarching species specific management measure for swordfish in the Indian Ocean, which limits the fishing capacity to 2007 levels. Other measures which also apply to swordfish include: recording of catch and effort information, recording of licensed and authorized foreign fishing vessels, regional observer program and maintaining a record of active fishing vessels (IOTC 2014).

There is no recovery plan in place but swordfish populations are healthy, except in the southwest Indian Ocean (IOTC 2017).

The Compliance Committee indicated that reporting of mandatory statistics is generally poor, due to incomplete and/or poorly documented data, although an improvement was noted in 2012 {IOTC 2013b}.There is no TAC in place but fishing effort has been reduced since effort limitations were put into place {IOTC 2013}.

Bycatch of seabirds and sea turtles in pelagic longline fisheries threatens some populations with extinction (Gilman, 2011). Bycatch of several vulnerable species groups has been documented in gillnet fisheries (e.g., Gilman et al., 2009). There are sea bird mitigation measures being used by some longline fleets in the Indian Ocean, which appear to have been successful at reducing interactions. The Indian Ocean Tuna Commission has implemented management measures for sea bird and sea turtles{IOTC 2013}.However, additional research on mitigation measures is warranted and continued monitoring of current mitigation measures and their effectiveness is needed.

Sharks and other fish species are also captured in longline fisheries. Total bycatch levels for the Indian Ocean longline fishery have been estimated to be 6%. Interactions with sharks continue to be problematic in this region because several large fleets use wire instead of monofilament leaders (making it difficult for sharks to escape capture).Blue and shortfin mako sharks are the two most commonly captured shark species {Adrill et al. 2013}.The Indian Ocean Tuna Commission has implemented some shark specific regulations {IOTC 2013}.However, additional research on mitigation measures is warranted as are additional management measures, such as bycatch limits.