Swordfish: water temperature and season

Deep by day, near the surface by night. Anglrithm scores swordfish at offshore spots on the Atlantic side and in the Keys. This page sets out what that score weighs and the cited studies behind it.

Water temperature

Evidence tier Well established

Swordfish tagged off Southeast Florida spent 87% of the day at 1,300-2,600 ft in 46-61 °F water and most of the night above 330 ft, so surface temperature does not constrain where they are. Most of those tags were out in fall and winter. We will not pretend an SST break decides a sword trip.

Season

Best Sep to Oct, by the score's season weight.

The score's season weight by month, from the studies cited in the species profile; the outlined months are at 90% of its peak or better.

What the score weighs

SeasonWell establishedkeeps 100%
CurrentSmall real effectkeeps 50%
WindSmall real effectkeeps 50%
SeasSmall real effectkeeps 50%
Wind vs currentSmall real effectkeeps 50%
LightReal, but localkeeps 100%

Why each tier

Season: Season is the strongest single predictor in most recreational datasets, because it carries water temperature, migration and spawning together. Shaw et al. 2021, PLOS ONE 16:e0257882.
Current: No study we found ties a current speed or direction to catch for any fish in this app. Current decides whether you can hold a bait where you want it and how a drift sets up: off Southeast Florida the Gulf Stream runs fast close to the coast, and deep-drop boats stay under power to hold position. Treat a current pattern as a fact about your fishing more than about the fish. Davis, Cudney & Blankinship 2017, Bulletin of Marine Science 93:539-555. Lerner et al. 2013, Transactions of the American Fisheries Society 142:95-104.
Wind: Wind has a measurable effect on fish movement, apparently through dissolved oxygen, but it is small. The larger effect in any personal log is on you: wind decides where you can fish and whether you go at all, so a wind pattern in your own data is at least as likely to be about your choices as about the fish. Milardi et al. 2019, Aquatic Ecology 53:251-263. Shaw et al. 2021, PLOS ONE 16:e0257882.
Seas: Sea state mostly decides whether the trip happens and whether you can fish it well. Treat a sea-state pattern in your own log as a fact about your fishing, not about the fish. No direct angling-scale study found; labelled from mechanism.
Wind vs current: Wind blowing against the current stands the seas up: shorter, steeper and more likely to break than the same wind over slack water, which decides how a drift sets up and how long a day stays fishable. That is physics about the water, not evidence about the fish; no study we found ties it to catch. U.S. Coast Pilot 4, Chapter 3 (opposing wind and current on the Gulf Stream: sharply higher, steeper seas that can break; mechanism only). No catch study found.
Light: Sun, cloud and rain change what you can see, not what the fish do. Sight fishing on the flats, and spotting fish, birds and weed offshore, depend on light getting into the water and on the glare coming off it, and how much sky and sun the surface throws back at you changes with the cloud, the wind and the height of the sun. On the flats with the sun up, light wind lets you see into the water, so for bonefish, permit, tarpon and redfish at inshore spots the score counts it in the hour's favour, fully at 4 mph or less and fading out by 7 mph; a glassy flat also shows you to the fish, so it is a local call, not a rule about the fish. This is about the angler, so trust it where you sight-fish. Local knowledge, Joe, October 6, 2026 (cloud, rain and sun) and October 14, 2026 (light wind at 4 mph or less). Santos et al. 2017, PLOS ONE 12:e0184776 (South Florida bonefishing is largely a sight-based fishery). Mobley 1999, Applied Optics 38:7442-7455. Cortese & Reimchen 2023, Biological Journal of the Linnean Society 138:132-140.

Each factor's weight is multiplied by its evidence tier: well established and real but local keep all of it, a small real effect keeps half, and a popular belief that is not supported keeps a fifth. Guidance from the studies sits beside the score, never in it.

From the research programs

Swordfish tagged off southeast Florida spent about 87 percent of daylight at 1,312 to 2,625 ft and nights mostly above 328 ft. Lerner et al., Transactions of the American Fisheries Society, 2013Best Bets places swordfish grid cells over 900 to 1,800 ft of water, a provisional default.
Daytime swordfish water was mostly 46 to 61 °F; at night they stayed mostly in 75 to 86 °F water. Lerner et al., Transactions of the American Fisheries Society, 2013
Brighter moons pushed swordfish deeper at night; around new moon they stayed above 246 ft most of the night. Lerner et al., Transactions of the American Fisheries Society, 2013
Southeast Florida swordfish grounds sit about 8 to 19 nm offshore over the 1,640 to 3,281 ft depth contours. Lerner et al., Transactions of the American Fisheries Society, 2013Best Bets places swordfish grid cells over 900 to 1,800 ft of water, a provisional default.
All tagged swordfish basked at the surface during daylight at times, larger fish more often. Lerner et al., Transactions of the American Fisheries Society, 2013

Findings in our own words from the programs linked, area and season only; cited, not endorsed. None of these lines is in the score.

The studies

Swordfish follow the deep prey layer day to day, while blue marlin and yellowfin rarely spend time below 200 m.
North Atlantic basin · field · full text read
Braun et al. 2023
Young swordfish center near the Caribbean in winter, move up the U.S. East Coast in spring and summer, and retreat south in fall.
western North Atlantic · field · full text read
Neilson et al. 2014
Billfish and swordfish spawn in summer offshore Gulf water, with larvae densest near the Loop Current edge and fronts.
northern Gulf of Mexico slope, Alabama to Texas (out of region) (outside South Florida) · field · full text read
Rooker et al. 2012
Mahi, wahoo and yellowfin patches match surface temperature patches, but swordfish patches match temperature at 200 m.
Gulf of Mexico (outside South Florida) · field · full text read
Kleisner et al. 2010
Tagged swordfish sat deeper at night near the full moon than near the new moon: a depth note for night baits, not a bite forecast.
western North Atlantic · field · full text re-read Oct 16, 2026
Loefer et al. 2007
Wahoo mostly stay above 50 m, while swordfish sit near the surface at night and drop to 700-800 m by day.
western North Atlantic and wider Caribbean · review · full text re-read Oct 16, 2026
Luckhurst 2007

The whole evidence library

Entries read in full text or published by an agency. Entries read only in their abstract are listed on the science page with their numbers withheld.

Where it is scored

Today's score at any of them is free with an account; every fish has a page like this one.

Display only, not for navigation. Every figure here names its source; check the NWS marine forecast and the posted rules before you leave the dock.