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Point Lobos Nudibranch Survey Project

September 19th 2007





Overview:

The BAUE Point Lobos Nudibranch Survey is an ongoing effort to quantify opisthobranch mollusc populations inside the diving areas at Point Lobos State Reserve. Four transects have been established on the Middle Reef in Whaler's cove where a representative set of opisthobranch species are surveyed periodically. Further, study participants are recording all species of opisthobranchs seen on dives in the park in order to build a comprehensive list of all species present inside the park.


Methods:

The primary focus of the study is our set of four transects on the Middle Reef where we sample fourteen species of opisthobranch. These were selected based upon abundance at Point Lobos, ease of identification and diversity of diet and life habits. It is hoped that these are representative of the opisthobranchs in the park and that their relative abundance will track that of similar species not in the study and also the health and diversity of prey items in each transect. The species included in the study are shown below.


Berthella californica


Cadlina luteomarginata


Dendronotus albus


Dialula sandiegensis


Doriopsilla albopunctata


Doris odhneri


Flabellina trilineata


Hermissenda crassicornis


Limacia cockerelli


Peltodoris nobilis


Phidiana hiltoni


Rostanga pulchra


Triopha catalinae


Tritonia festiva


Each transect is roughly 20 feet long by 10 feet high on a vertical wall. The size was chosen to allow each transect to be carefully surveyed within 20 minutes. The transects were selected based upon several criteria. First, they needed to be readily identifiable from natural landmarks as we did not wish to install any hardware on the reef. Second, we wanted a reasonably representative sample of reef in the Middle Reef area and finally, we had observed each transect to be rich in opisthobranchs. A map of the transects can be found here.

Note that the transects are numbered 1, 2, 4 and 5. Originally there were five transects but number 3 was removed due to difficulty sampling it during the summer in heavy kelp growth.

Transect One is a west facing wall on the north end of the Middle Reef. The southern boundary is the crack which extends through the reef to the east side. The crack itself is not part of the transect. The northern boundary is the northern tip of the reef which features a knob shaped overhang. The transect starts at the sand at a depth of about 60 feet and extends up from there 10 feet from the bottom. The total length of the transect is roughly 20 feet.

Transect Two is an east facing wall with significant overhang on the north end of the Middle Reef. The southern boundary is the crack mentioned in Transect One. Again, the crack itself is not part of the transect. The northern limit is again the northern tip of the reef. Vertically the transect starts at the sand at about 60 feet and extends up from there 10 feet.

Transect Four is a notch in the west wall of the middle reef, about 100 feet south of Transect One. The left side of the notch is a south facing vertical wall shaped something like a keystone. It is only a foot or two wide at it's base and about 12 feet wide at the top which is about 15 feet from the bottom. The right side of the transect is a square wall about 8 feet wide and 10 feet high measuring from the sand.

Transect Five is a west facing reef with significant overhang about 100 feet south of Transect Four. Its main feature is a cave which narrows to about a 2 foot diameter hole extending to the other side of the middle reef. In most places the overhang/cave is extends about 3 feet into the reef. The northern and southern boundaries of the transect are the edges of this cave. The transect extends from the sand at a depth of about 40 feet up 10 feet. The top of the reef above the cave is somewhat indistinct.

There is an ongoing mapping project on the Middle Reef which we hope to use to provide more exact descriptions of the four transects. For now participants are taught the boundaries of the transects by the project leaders.

Transects are sampled at a quarterly frequency at a minimum with additional surveys done based on availability of the team members. Surveyors record a count of the number of each species in the study seen in the transect, the start and stop time of their survey for each transect,  water temperature and estimates for surge and visibility. The intent is for each transect survey to be completed in about 20 minutes to maintain consistency from survey to survey.

Additionally on all project dives at Point Lobos team members will record the presence of all species of opisthobranchs seen on their dives. In this way we hope to make a complete list of opisthobranchs in the park. These surveys are not limited to the Middle Reef but are conducted in the entirety of the diving area of the park.


Current Data:

A spreadsheet with our current transect data to date can be found here.

Below is our complete list of all opisthobranchs seen in the diving area of the park.

Acanthodoris hudsoni
Adalaria jannae
Aegires albopunctatus
Aldisa albomarginata
Aldisa cooperi
Aldisa sanguinea
Ancula gibbosa
Berthella californica
Cadlina flavomaculata
Cadlina limbaughorum
Cadlina luteomarginata
Cadlina modesta/Cadlina sparsa
Conualevia alba
Corambe pacifica
Cuthona divae
Cuthona fulgens
Dendronotus albus
Dendronotus diversicolor
Dendronotus frodosus
Dendronotus subramosus
Dialula sandiegensis
Diaphorodoris lirulaticauda
Dirona albolineata
Doriopsilla albopunctata
Doriopsilla spaldingi
Doris odhneri
Doris montereyensis
Doto amyra
Doto columbiana
Elysia hedgpethi
Flabellina trilineata
Flabellina iodinea
Geitodoris heathi
Hallaxa chani
Hermissenda crassicornis
Limacia cockerelli
Melibe leonina
Okenia rosacea
Okenia sp.
Onchidoris muricata
Peltodoris nobilis
Phidiana hiltoni
Rostanga pulchra
Tochuina tetraqueta
Trapania velox
Triopha catalinae
Triopha maculata
Tritonia festiva


Observations:

While the real value of this study may only become apparent over time as we build up body of data there are a few items of particular interest. First, there are several of our chosen species which have thus far been either absent or very rare from our transects. These are Dendronotus albus, Doris odhneri, Flabellina trilineata and Phidiana hiltoni. These species were included on our list since we have regularly observed them in the past at Point Lobos. It isn't clear why we haven't seen them yet on the transects. We have seen all of them with some frequency outside the transects in similar looking areas.

Also missing from our transects and our complete species list are a number of fairly common species. As with our study list most of these missing animals are aeolids or denronotids. For instance we have not found few examples of Cuthona, Doto or Eubranchus which are common in other areas of Monterey or Carmel Bay.

We have also been surprised to find several species in relative abundance in our transects which we had previously considered to be relatively rare. This include Aegiris albopunctatus and Diaphorodoris lirulaticuada. These two species are very small, usually less than 5 mm, which may account for our having missed them previously. Other species which are proving to be common but which are not included in the study are Cadlina flavomaculata, Cadlina modesta/sparsa (these two are hard to distinguish underwater) and Geitodoris heathi.

Update on 10-Oct-2007: John and I found Doto columbiana in a shallow area of the middle reef so that genus has now been seen. Also we finally found Flabellina trilineata in one of our transects (transect 4). Also Corambe pacifica was observed for the first time just outside transect 2.

Update on 20-April-2008: Allison, Rob and John found an mysterious white dorid near Twin peaks, which was subsequently ID'd as Aldisa albomarginata. We also found a yellow slug on Transect 1 which was later ID'd as Hallaxa chani. Two new (to us and the park) species in one day; not bad :-).

Update on 04-May-2008: Allison and Rob spotted Cuthona fulgens near Twin Peaks, adding another Cuthona species to the list.

Update on 11-May-2008: Allison and Rob found a mystery slug near Twin Peaks tentatively thought to be an unknown/undescribed species of Okenia.
Update on 12-Oct-2008: Allison and Rob spotted Cuthona divae and Doto amyra at Twin Peaks, adding 2 more species to the list.
Update on 2-July-2010: (DCB) Added Conualevia alba, Aldisa cooperi, Okenia sp., Dendronotus subramosus and Trapania velox based on recent observations. Updated the text a bit.



Participants:

Name Roll
Clinton Bauder Science Lead/Photographer
John Heimann Project Lead
Allison Lee Surveyor
Robert Lee Surveyor/Photographer
Matt Vieta Surveyor
Michael Jimenez Surveyor/Photographer
Jason Warshawsky Surveyor
Alicia Hermosillo Science Advisor/Surveyor
Roberto Chavez Arce Videographer
Mark Lloyd Surveyor
Dionna House Surveyor
Ildiko Frank Surveyor
Anibal Mata-Sol Surveyor
David Chamberlin Surveyor
Nick Radov Surveyor
Brian Gilpin Surveyor
Josh Umstead Surveyor
Kevin Dow Surveyor
Suzanne Baird Surveyor


Additional Resources:

The Sea Slug Forum
The Slug Site
Eastern Pacific Nudibranchs by David W. Behrens and Alicia Hermosillo
Point Lobos State Reserve
Kickoff Meeting Slides (A bit out of date now)
Nudibranch Survey Video by Roberto Chavez Arce taken during Alicia Hermosillo's visit.