Modeling the Spatial Distribution of Swordfish (Xiphias gladius) Using Fishery and Remote Sensing Data: Approach and Resolution

Abstract

Swordfish, Xiphias gladius (Linnaeus, 1758), is a commercially important species that is widely distributed throughout three oceans. This species inhabits oceanic waters with preferred environmental ranges and migrates vertically to the surface layer for feeding. However, the spatial distribution pattern and habitat preferences of swordfish have been rarely studied in the Pacific Ocean due to the wide geographic range of this species. This study examined the spatial distribution and preferred ranges of environmental variables for swordfish using two approaches, generalized additive models and habitat suitability index methods, with different spatio-temporal data resolution scales. Results indicated that sea surface temperature is the most important factor determining swordfish spatial distribution. Habitat spatial pattern and preferred environmental ranges, estimated using various modeling approaches, were robust relative to the spatio-temporal data resolution scales. The models were validated by examining the consistency between predictions and untrained actual observations, which all predicted a high relative density of swordfish in the tropical waters of the central Pacific Ocean, with no obvious seasonal movement. Results from this study, based on fishery and remote sensing data with wide spatial coverage, could benefit the conservation and management of fisheries for highly migratory species such as swordfish and tuna.

Nursery origin and population connectivity of swordfish Xiphias gladius in the North Pacific Ocean

“…The CENPO has been referred to as a zone of high swordfish abundance (Hinton & Deriso, 1998;Su et al, 2020) and the observation that swordfish reproduction occurs year-round in the equatorial Pacific Ocean (Nishikawa et al, 1985;Palko et al, 1981) indicates that the CENPO nursery has the potential to be a large contributor of swordfish recruits to the NPO. This is of particular interest for future stock assessments and management as the Hawaiian fishery provides some 38% of the domestic catch of swordfish (Ito & Childers, 2014).…”

Modeling the importance of subsurface environmental variables in driving swordfish (Xiphias gladius) catchability in the Western Indian Ocean

“…Based on the results of previous studies on the environmental preferences of swordfish, surface environmental variables, including temperature, salinity, dissolved oxygen, net primary productivity, northward and eastward sea water velocity, and the two‐dimensional variable mixed layer depth, were selected as candidates for describing the surface habitat of swordfish in the Western Indian Ocean (Brodie et al, 2018; Chang et al, 2012; Evans et al, 2014; Scales et al, 2017; Su et al, 2020). For the subsurface environment, water temperature, salinity, net primary production, and dissolved oxygen were selected as critical variables to be gradually added to the model at 100 m intervals to a maximum depth of 500 m. All marine environmental data were downloaded from the COPERNICUS website (http://marine.copernicus.eu/) using monthly averaged data from 2017 to 2019 and coupled with species occurrence data.…”

Philopatry as a Tool to Define Tentative Closed Migration Cycles and Conservation Areas for Large Pelagic Fishes in the Pacific

“…3.1.6. Swordfish (Xiphias gladius) Swordfish (Xiphias gladius) has the widest distribution of all billfishes [73,74] and can be found in all three oceans [75] throughout temperate, subtropical and tropical regions, [76] mainly between 45 • N and 45 • S [73,74]. A study by Evans et al (2014) [77] suggested that most of the individuals tagged spent the vast majority of their lifetime within the 15 and 45 • S latitudinal range.…”

“…There is a broad and quasi-continuous maturation-spawning region associated with the warm waters of the central-western intertropical band [83]. However, information is lacking about this species' spatial structure, spawning grounds, habitat preferences and population composition [75,77,84]. [72].…”