March 17, 2024

Guide to egg masses of sea slugs from the Northeastern Pacific

@thetidepooler recently asked if I knew of any guides to egg masses of sea slugs from California, and I thought of this wonderful online guide put together a few years ago by avid diver and talented photographer Merry Passage, with contributions from her husband and equally avid and talented underwater photographer Phil Garner (@maxbottomtime):

Some of the images in Merry's guide made their way into Behrens et al. (2022) guidebook, and as with all guides using scientific names, it doesn't take long for some of the nomenclature to change, so anyone not recognizing the use of a particular genus or species may want to consult WoRMS (, which iNaturalist relies on.

I wish I had thought of spreading the word about Merry's guide sooner on iNaturalist; in any case, thank you again, Merry, for your efforts in putting this together!

OK, it might be time to make an iNat Project for Egg masses of NE Pacific heterobranchs. If one of you wants to start one before I can get to it, that would be great!


Posted on March 17, 2024 02:18 PM by jeffgoddard jeffgoddard | 7 comments | Leave a comment

July 10, 2023

Nudibranchs observed by William Pence and Douglas Mason during five decades at Pillar Point, California

The broad siltstone bench at Pillar Point is one of the most highly visited intertidal sites in California. It’s easily accessible, close to the San Francisco Bay Area, and with recreational users in mind, was intentionally excluded from the system of Marine Protected Areas established in California starting in 2007. Since 2012 it has also been a hub of community science, with a popular and ongoing biodiversity monitoring program coordinated by the California Academy of Sciences and iNaturalist (

Well before these milestones - including the launch of iNaturalist out of the Bay Area in 2008 - two dedicated biology teachers from California High School in San Ramon had quietly started recording the numbers and species of nudibranchs at Pillar Point. From late 1988 to late 1996, Bill Pence and his former student Douglas Mason, out of pure interest and curiosity, and sometimes accompanied by a few of their students, conducted 103 surveys, frequently twice a month, at Pillar Point, focusing their observations on a set of 10 tide pools on the outer reaches of the bench.

“The original motivation for me was simply to be out in the marine environment interacting with those fascinating creatures and it wasn't until later that questions regarding nudibranch seasonality and abundances occurred to Bill and me, and we started recording data. Our plan then was to visit Pillar Point regularly (twice per month if we could) and record nudibranch species and numbers. In the beginning, we rarely encountered other people out on the shelf and usually had the place to ourselves. I am not sure that we knew how we were going to use the data, but we hoped we might see patterns that would help us understand why, for example, we saw hundreds of Doriopsilla albopunctata in some months and very few of them in other months (I was getting my degree in philosophy at the time and had only taken a few biology courses-- much later I got a degree in biology). Bill and I had hundreds of hours of direct physical and intellectual pleasure gathering that data.”

“We were generally on our hands and knees, slowly crawling through the pools, combing algae, looking under ledges, and in crevices. Since many ‘branchs are tiny (e.g., species of Doto and Cuthona), this type of searching was slow and methodical, and we often used hand lenses for better identification. For difficult identifications, we collected the ‘branch and at the end of our collecting period looked at it under a dissecting scope we had brought with us into the field.”

Bill had been introduced to the richness of the rocky intertidal on an Invertebrate Zoology field trip to Pigeon Point as a freshman at San Jose State University, and Douglas had first been introduced to Pillar Point on an Invertebrate Zoology field trip under Dr. Ned Lyke at CSU Hayward (now CSU East Bay). First Bill, then Douglas carried on that tradition throughout their own teaching careers, which overlapped for years at California High School.

In 2007, soon after I had received a grant to resurvey three sites of historical, multi-year surveys of nudibranchs in California, I happened to meet Ned Lyke at a memorial symposium honoring Dr. Cadet Hand, former Director of the Bodega Marine Laboratory. Ned told me about two teachers - one a former student of his - who had nearly a decade’s worth of regularly collected data on nudibranchs from Pillar Point. He put me in touch with Bill and Douglas, who had been fretting now and then about what to do with their data, and not only did they share their data with me, they also offered to restart sampling Pillar Point as part of the new study!

Long story short, Bill and Douglas, now assisted by Phil Dobry, one of their former students, added another three years to their Pillar Point dataset - and then extended that to 2020! If their sampling frequency at Pillar Point became reduced, it was only because these now unassuming legends had spread out along the coast to explore new sites (and in the process I am certain, regain some of the peace and quiet familiar from their early years at Pillar Point). All years combined, Bill and Douglas made 137 trips to Pillar Point in 100 different months and recorded 14,718 individuals in 56 species (see Table 1: These numbers are remarkable because they were all nudibranchs and none of the other types of sea slugs, like bubble snails and sacoglossans, that can numerically dominate some sites.

They found the first Phidiana hiltoni known from Pillar Point (in January 1991), recorded exceedingly high densities of Doriopsilla albopunctata s.l. in summer 1989, and during the 2015-16 El Niño Douglas recorded unprecedented numbers of Okenia rosacea.

Bill and Douglas have not only provided an invaluable baseline for future ecological studies on nudibranchs in California, they have built, one identification at a time, a legacy among dedicated California ‘branchers.

Bill and Douglas were included as authors on a scientific 2011 paper in Limnology and Oceanography which relied extensively on their data from Pillar Point through 2008 (see:, and the three of us plan a paper focused on the long-term results from Pillar Point. In addition, Bill and Douglas’ results from other sites have contributed significantly to papers published on nudibranch range shifts on the west coast associated with the marine heat waves of 2014-16:

@mcduck, @anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, @imlichentoday, @marisa_a, @arheyman, @noiselessowl, @jeffhamann

Posted on July 10, 2023 03:48 PM by jeffgoddard jeffgoddard | 3 comments | Leave a comment

July 03, 2023

Nudibranchs and allies from Cave Landing, San Luis Obispo Co., CA

Here is a link to a site description and summary of nudibranchs and allies that Gary McDonald and I have found over the years at one of our favorite tide-pooling spots, located next to Avila Beach:

As we describe inside, access to our old study site at Cave Landing is currently virtually impossible except by boat or kayak, so please exercise caution!

@mcduck, @anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, @alanarama3, @alex_bairstow, @imlichentoday, @skatingflamingo, @marisa_a, @arheyman, @noiselessowl, @jeffhamann

Posted on July 03, 2023 02:11 PM by jeffgoddard jeffgoddard | 1 comment | Leave a comment

June 26, 2023

Nudibranchs and allies from Hazard Canyon Reef, San Luis Obispo Co., CA, 1999-2021

Below is a link to the third of four papers planned with my twin sons on nudibranchs and allies from Santa Barbara and San Luis Obispo Counties, this one Hazard Canyon Reef, an intertidal site in Montana de Oro State Park well known to users of iNaturalist in the region. This paper follows the same general format as the previous two papers, but includes a table (on p. 546) listing species found by other observers (including @marisa_a, @arheyman, @noiselessowl, @anudibranchmom, @kueda, @dpom, and @craigahoover) at Hazard Canyon and in the subtidal nearby that we did not observe during our study.

In our 50 total trips to Hazard Canyon we recorded 5919 individuals of heterobranch sea slugs from 63 species, 57 of which were nudibranchs. In one additional trip, on 5 June 2023, I found another 60 individuals from 16 species, none of which were new additions to our overall list.

@anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, @alanarama3, @alex_bairstow, @imlichentoday, @skatingflamingo, @marisa_a, @arheyman, @noiselessowl

Posted on June 26, 2023 01:39 PM by jeffgoddard jeffgoddard | 6 comments | Leave a comment

June 23, 2023

Nudibranchs and allies from Tar Pits Reef, Carpinteria, CA, 2008–2020

Below is a link to the second of four papers planned with my twin sons on nudibranchs and allies from Santa Barbara and San Luis Obispo Counties, this one on Tar Pits Reef in Carpinteria.

Tar Pits Reef is a small, but rich intertidal site for nudibranchs, especially in the late spring, at the height of the blooms of epiphytic hydroids but before inundation of parts of the reef by sand in late summer. During our 40 total trips to this site we recorded 3590 total individuals in 52 species of heterobranch sea slugs, 45 of which were nudibranchs. The reef is also the type locality for Pacifia goddardi, which was described and named after me in 2010 by Terry Gosliner and which has since been found subtidally at Santa Cruz and Anacapa Islands, Malibu, and Palos Verdes. Craig Hoover and I published a paper of the distribution, seasonality and diet of P. goddardi (as Flabellina goddardi) in 2016, and I have also provided below a link to that paper.

Since 2020 we have sampled Tar Pits Reef for sea slugs twice more, once in April 2021, when Ziggy added Eubranchus sp. 1 of Behrens et al. (2022) to our list for the reef (and extended its range from La Jolla:, and most recently on a pre-dawn trip with @alanarama3 on the 4th of this month.

Link to Goddard and sons (2021):

Link to Goddard and Hoover (2016):

@anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, @alanarama3, @alex_bairstow, @imlichentoday, @skatingflamingo

Posted on June 23, 2023 03:09 PM by jeffgoddard jeffgoddard | 4 comments | Leave a comment

June 22, 2023

Nudibranchs and allies from Naples Point, Santa Barbara Co., CA, 2002-2019

The boulder field at Naples Point, on Santa Barbara's Gaviota coast, was one of my family's go-to sites for nudibranchs while we lived at Midland School in the Santa Ynez Valley. My twin sons Ziggy and Will began accompanying me in my search for nudibranchs there in 2008, quickly developed laser-sharp search images, and were soon contributing significantly to the results. Together, we wrote and published the scientific paper linked below, the first of four planned papers, one each on the heterobranch sea slugs from a different site in Santa Barbara and San Luis Obispo Counties. Will and Ziggy are fine writers and editors.

In our paper we first review the literature on the heterobranchs known from Santa Barbara County. We then describe our study site at Naples Point in detail and present our results on the species composition, abundance, and seasonal and interannual variation in abundance. During this study we recorded 12,193 individuals from 55 species, 48 of which were nudibranchs. These are listed in Table 1, on pp. 284-85. Since 2019 and through 9 June 2023, I have made seven more trips to Naples Point and recording a total of 223 additional individuals and no additional species.

Heterobranchs are often sparse and difficult to find at Naples Point, usually requiring a lot of rock rolling (and righting!), and many of the species are small. But sometimes they were abundant, large, and couldn't be missed, as when Black sea hares and Gould's bubble snails just exploded in abundance during the 2014-2016 marine heat wave.

Here's our paper:

@anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, @alanarama3, @alex_bairstow, @imlichentoday, @skatingflamingo

Posted on June 22, 2023 05:24 PM by jeffgoddard jeffgoddard | 2 comments | Leave a comment

June 21, 2023

Intertidal nudibranch sea slugs from Scott Creek, Santa Cruz County, California, 1975-2015

A recent inquiry from @joepaquin about Scott Creek, CA as a site for nudibranchs prompted me to write a summary of results of a long-term study of nudibranchs at Scott Creek that I started as an undergrad at UC Santa Cruz. At first glance my Scott Creek study site may not appear to be particularly promising for nudibranchs, especially compared to larger and better known sites in the region, like Carmel Point, Pillar Point, Fitzgerald Marine Reserve, or Duxbury Reef. But over the years and decades, the shallow pools with their low, overhanging ledges revealed a rich biodiversity, drawing me back time and again. The full site is best observed on tides falling below -1’ when the swell isn’t too large, but many productive pools are exposed on any minus tide. The only caveat is that one needs to move along on one’s knees a lot here to see what’s under all those low ledges, an activity I'm less inclined to do these days, after my 55 years of searching for nudibranchs. On the other hand, the walk to the site, though not too long, is just long enough to ensure that sometimes you’ll be the only person present, a real gift on a calm foggy morning between Pacific tides so close to the hustle and bustle of the Bay Area.

So, for your interest, @joepaquin, and other aficionados of intertidal nudibranchs in central CA, including @mcduck, @anudibranchmom, @chilipossum, @passiflora4, @chloe_and_trevor, @kestrel, @rebeccafay, @nudibitch, @kueda, @dpom, @craigahoover, @lemurdillo, @lorri-gong, @lutea11, here is where you can find a summary of my study of nudibranchs at Scott Creek:

Thanks to @anudibranchmom for the suggestion on how to make my pdf publicly available

Posted on June 21, 2023 09:25 PM by jeffgoddard jeffgoddard | 8 comments | Leave a comment


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