The evidence behind the labels on every species row
Every species this site tracks carries a rarity label — Daily, Regular, Uncommon, Very rare, and so on. Those labels decide which sightings get flagged as notable on the homepage, so they need to mean something more than a guess. This page shows the working.
The short version: "rare" here means rare in the published record for the Southern California Bight — the stretch of coast from Point Conception to the Mexican border — as measured by line-transect surveys, passive acoustic monitoring, and federal stock assessments. It does not mean "the boats haven't seen one this week."
The easiest mistake in whale-watching copy is to rank species by how impressive they are rather than how likely you are to see one. A blue whale is the largest animal that has ever lived, so it feels like a once-in-a-lifetime encounter. In the Southern California Bight in August, it isn't — it is the most seasonally predictable large whale in the water.
The clearest evidence comes from Campbell et al. (2015), who analysed 37 quarterly line-transect cruises run across the Bight between July 2004 and November 2013. Of 79 on-effort blue whale sightings in that decade, 62 fell in summer. Across those same ten years of survey effort, blue whales were recorded once in winter and once in spring. Expressed as density, the survey found roughly forty times as many blue whales per unit area in summer as in winter.
So the honest label for a blue whale is not "rare visitor" but "Reliable in summer — June to October, peak July–September." Reliable is not the same as guaranteed: densities were higher in the early and mid-1990s, part of the population appears to have shifted north and offshore since the late 1990s, and two years in the middle of the survey decade were notably poor. But a blue whale off Long Beach in August is a species behaving exactly as expected.
The ladder used across the site runs, loosely, from most to least expected:
Four kinds of evidence sit behind the labels, and they answer different questions.
Line-transect surveys answer "how many animals are in this water, in this season?" Campbell et al. 2015 (Deep-Sea Research II 112:143–157) is the backbone: ten years of quarterly CalCOFI cruises covering the Bight specifically, rather than the whole US West Coast. It is the reason the seasonal labels have shape.
Federal stock assessments answer "how many exist at all, and is that changing?" NOAA's U.S. Pacific Marine Mammal Stock Assessments give abundance estimates and, importantly, say plainly when the data cannot support a trend claim.
Passive acoustic monitoring answers "were they here when nobody was looking?" Alksne et al. 2024 (Diversity and Distributions 30(9)) draws on recordings from 14 sites between 2005 and 2021 — continuous coverage a ship survey cannot match.
Shore-based census and operator logs answer "what actually happened this season?" The ACS/LA gray whale census at Point Vicente has counted the migration from land for decades, and operators' own long-run trip reports are the only record of how often a day boat encounters a given species.
This is the most consequential number on the site, because the gray whale is the winter mainstay: anyone booking a December-to-April trip is booking to see this species. The eastern North Pacific population peaked at roughly 27,000 animals around 2016, two decades after being removed from the Endangered Species list in 1994. NOAA's 2025 estimate is about 13,000, with models placing it most likely between 11,700 and 14,500 — roughly a 52% fall, and the lowest figure since the 1970s.
An Unusual Mortality Event ran from 17 December 2018 to 9 November 2023, with 690 strandings recorded — 347 in the United States, 316 in Mexico and 27 in Canada. Estimates taken immediately after it ended suggested a rebound was under way; the winter 2025 count instead showed the decline continuing. Calf production is the sharper signal: roughly 85 calves passed central California in 2025, the lowest since records began in 1994.
The shore-based record from Southern California is consistent with that picture, though it measures a different thing. The ACS/LA census at Point Vicente counts whales passing one headland; in 2024–25 it logged 130 southbound whales with zero southbound calves, and 485 northbound with 8 calves — 1.6% of northbound migrants. Against ACS's own published historical ranges — southbound has varied between 293 and 1,902, northbound between 521 and 3,412 — that season sits below the bottom of both.
These two sets of figures are not the same quantity and must not be read as one series. NOAA's ~13,000 is a model-based abundance estimate for the entire eastern North Pacific population. The ACS numbers are a count — an index of how many whales passed a single point of coastline while observers were watching. They agree in direction; they are not interchangeable.
None of this makes a winter trip a poor bet. The migration is still the most dependable whale-watching event of the Southern California year, which is why the label reads "Common in season — late Dec to mid-Apr." But "abundant" is no longer an honest word for it, so the site does not use one.
This is the species where the survey data is most dramatic and the honest conclusion is most restrained. Campbell et al. found it was the only one of six study species with a statistically significant trend inside the Bight: density fell from 138 animals per 1,000 km² in 2004 to 4.6 by 2012, a decline of roughly 22.5% a year. The acoustic record shows a step change after the 2014–16 marine heatwave.
But the stock as a whole — estimated at about 34,999 animals in 2018 — shows no long-term trend. The dolphins moved; they did not disappear. So the label is "Uncommon — winter and spring; much scarcer than 20 years ago", and this site does not describe them as a declining species.
Risso's are often assumed to be in decline here. NOAA's 2023 assessment does not support that: it describes them as commonly seen on the shelf in the Southern California Bight, with insufficient data to evaluate potential trends, on an estimated stock of about 6,336 animals. The longer history runs the other way — they were rarely encountered off Southern California in the late 1950s and increased through the 1972–75 period.
The most striking chapter is at Santa Catalina Island. Short-finned pilot whales were once common off Southern California, with an apparently resident population around Catalina; after the 1982–83 El Niño they virtually disappeared. Risso's dolphins, seldom seen there before, increased from 1987 onward. One species vacated a niche and another moved into it, and the day boats have been reporting the result ever since. It is also why the short-finned pilot whale — a species people assume is a local fixture — carries a "Very rare" label today.
One correction that follows from the same reading: a "peak in fall" for Risso's is not supported by the literature, which points to cooler months generally. The label reads "Regular — year-round, more often in cooler months."
Only two Bryde's whales were confirmed off southern California in five decades (Smultea et al. 2012, Aquatic Mammals 38(1):92–97). The January 1963 animal off La Jolla was originally identified as a fin whale, and five further survey records could only ever be logged as "sei or Bryde's" — the two species are frequently inseparable at sea. NOAA's 2023 assessment counts seven or more in southern and central California across 1991–2014.
Acoustics add a twist: Bryde's calls were absent from Southern California recordings in 2000–01, then detected in every year from 2003 to 2010, from summer through early winter — consistent with a northward range expansion. The label is "Very rare — celebrate."
The identification problem is also why this site's scraper refuses to resolve an operator's "sei or Bryde's" entry to either species. It goes to a review queue instead of quietly becoming the rarest baleen record of the year. See the methodology page for how that queue works.
Sperm whales are present in California waters year-round, on a stock estimated at about 2,606 animals in 2018, and the region has real history with them: 176 were Discovery-tagged off southern California in the winters of 1962–1970. On paper, that is not a rare animal.
In practice they work the deep basins and the slope, while day boats work the shelf. Operator records make the point better than any density figure: a Dana Point operator logged sperm whales in 2023, 2024, 2025 and 2026 — and before that, not since 2014. A San Diego sighting in September 2025 was reported as the first since 2011. Because this site describes what a day-boat passenger can expect, the label is "Very rare — celebrate."
There are thought to be around 30 North Pacific right whales in the eastern North Pacific. Southern California has two records from 2017, off La Jolla and off Malibu — and the La Jolla animal was initially logged as a gray whale. A single confirmed sighting would be the most significant cetacean record in the region in years, which is why its label is "Exceptional — once in a generation" and why it outranks everything else in the site's alert logic regardless of how many animals were counted.
Common dolphins earn the "Daily" label on volume: roughly 168,000 animals in the CalCOFI study area alone, present in every season the surveys covered. Bottlenose dolphins are labelled "Regular — year-round, close inshore" for a geographic reason: the California coastal stock spends 99% of its time within 500 m of the beach and 90% within 250 m — which is precisely where the boats run. Humpbacks are "Regular" and improving: the California/Oregon population of roughly 5,000 has grown at about 7–8% a year since the late 1980s. Fin whales likewise show higher densities in the Bight than surveys recorded across 1991–2008.
Some labels rest on far less than others. Rather than dress those up, here is where the confidence drops:
The site recognises a fixed allowlist of 23 species. Some plausible-sounding omissions are deliberate:
The allowlist is not a filter that throws away surprises. A species string outside it — including a genuine first record — is captured in a review queue for a human to read, rather than being force-fitted to the nearest known species or silently discarded. It simply does not enter the published counts until someone confirms it.
Every figure on this page is decadal. Survey densities, stock estimates and trend rates describe the Southern California Bight averaged over years — in some cases over half a century. The numbers on the homepage describe what boats reported today.
These two things must never be read as one. A rarity label cannot tell you whether the animals are out there this afternoon, and a day's sighting count cannot tell you whether a species is common in the region. A blank week for gray whales in February is weather and luck; a decade of survey data is what makes "common in season" true anyway. Conversely, an exceptional day for Pacific white-sided dolphins does not undo a 22.5%-a-year decline in the survey record.
For how today's counts are gathered and scored, see the methodology page.
Population figures on this page were verified against the cited sources on2 August 2026. NOAA stock assessments are republished annually — if that date is more than a year old, treat the numbers as indicative and follow the links for current figures.
If you think a label is wrong, or you have a published source that contradicts one, please get in touch. Corrections are welcome and will be made.