Biological State and Trend
Habitat and Biology
Depth zone: Abyssal ( >1000m). Horizontal distribution: Oceanic. Vertical distribution: Pelagic.
Jurisdictional distribution: Highly migratory
Considered a single stock: Yes
Striped marlin (Kajikia audax
) occur throughout the Pacific Ocean between about 45°N and 45°S. Significant effort has been devoted to understanding the stock structure of striped marlin in the Pacific Ocean, which is now moderately well known. It has been clear for some years that there are a number of stocks. Information on the movements of striped marlin is limited. Fish tagged with conventional dart tags and released off the tip of the Baja California peninsula have generally been recaptured near where they were tagged, but some have been recaptured around the Revillagigedo Islands, a few around Hawaii, and one near Norfolk Island. Tagging studies of striped marlin in the Pacific conducted using pop-off satellite tags indicated that there is essentially no mixing of tagged fish among tagging areas and that striped marlin maintain site fidelity. Recent results of analyses of fisheries and genetic data indicate that the northern EPO is home to a single stock, though there may be a seasonal low-level presence of juveniles from a more westerly Hawaii/Japan stock.
The assessment on which this report was based is for the stock of striped marlin in the eastern Pacific Ocean (EPO) region lying north of 10°S, east of about 145°W north of the equator, and east of about 165°W south of the equator. The assessment of this stock was conducted using Stock Synthesis, with data updated as of 30 October 2010.
Historically, the majority of the catch in the EPO was taken by longline fisheries; however, removals by recreational fisheries have become more important in recent years (Figure I-1).
|Figure I-1: Landings of striped marlin from the northern EPO by longline and recreational fisheries, 1954-2012. Due to unreported catches by recreational fisheries, estimates for 2009-2013 are minimums. |
Longline fisheries expanded into the EPO beginning in the mid-1950s, and they extended throughout the region by the late 1960s. Except for a few years in the late 1960s to early 1970s in the northern EPO, these fisheries did not target billfish.
Fishing by smaller longline vessels targeting tuna and other species off Central America, for which catch data are not available, appears to have increased recently. The shifting patterns of areas fished and targeting practices increase the difficulties encountered when using fisheries data in analyses of stock status and trends. These difficulties are exacerbated when analyzing species which are not principal targets of the fishery, and further exacerbated when the total catch of the species by all fisheries is not known.
The fishing effort by large longline vessels in the northern EPO has increased by about 20%, and the catch of striped marlin by longlines by about 70%, since 2010. This differential may be due to increasing striped marlin biomass or such as spatial/temporal shifts in fisheries resulting in increased availability of striped marlin to the longline fishery.
The most recent report of catch by the recreational fishery was for 1990-2007 and included preliminary data for 2008. It is estimated that this fishery makes the majority of the catch of striped marlin in the northern EPO. Based on recent analyses of other billfish species, it appears that catches of billfish, including striped marlin, by components of the smaller-vessel longline fishery operating off Central America have not been reported. Therefore the total catch of striped marlin in the EPO, and thus the total impact of fishing on the stock since about 2008-2009, is not known.
Since catches of striped marlin and fishing effort have increased in the large-vessel longline fishery, and because there is uncertainty in the estimated total catch of striped marlin in the EPO since at least 2008, the trends in spawning and total biomass of striped marlin in the EPO are unknown. Efforts have and are being made to obtain reliable catch data from all fisheries. Until the data are available and updated, and a review of the status of striped marlin in the EPO is completed, it is recommended that a precautionary approach be adopted, and that fishing effort directed at striped marlin in the EPO not be increased.
See also fishery fact sheet:EPO Tunas and billfishes fishery
Overall Assessment ResultsKey results of the assessment were that
- The stock is not overfished.
- Overfishing is not occurring.
- The spawning stock biomass has been increasing and is above that expected to support MSY catch.
- Catches in recent years have remained at about half the MSY catch level. If fishing effort and harvests had continued at levels near 2010 levels, it was expected that the biomass of the stock would continue to increase over the near term.