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Alternative title

Recovery of a sea star from a historical mass mortality event

Date Permissions Signed


Date of Award

Summer 2021

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Science (MS)



First Advisor

Miner, Benjamin G., 1972-

Second Advisor

Acevedo-Gutiérrez, Alejandro, 1964-

Third Advisor

Brodhagen, Marion (Marion L.)

Fourth Advisor

Donovan, Deborah Anne, 1964


In 1978 populations of a charismatic and abundant intertidal sea star Heliaster kubiniji (Xantus) declined throughout the Gulf of California. Two years after this mass-mortality event, researchers found very low densities of H. kubiniji at many sites throughout the region and concluded that the species had not recovered. To my knowledge H. kubiniji densities in the Gulf of California have not been formally surveyed since the 1980 mass-mortality event. Although intertidal sampling has sporadically occurred within the region, many questions regarding invertebrate populations remain unanswered. To better understand and predict the recovery of echinoderms from mass-mortality events, I returned to historically sampled sites in the Mexican states of Baja California and Baja California Sur to assess recovery almost 40 years after the mortality event. I conducted vertical transects on rocky intertidal beaches at 13 sites. Densities of H. kubiniji were found by dividing the total area surveyed by the number of H. kubiniji found. I also conducted interviews with community members collecting intertidal organisms to learn more about the local abundance, as well as whether these sea stars were being collected for sale as curios. The results of these surveys as they relate to the recovery of H. kubiniji are discussed in Chapter 1. During transect surveys to quantify the presence of H. kubiniji, as well as snorkel surveys at each site, I documented the presence and density of several other member of the Gulf intertidal community. I analyzed historical field notes for observations of the additional species at sites on the Baja California peninsula. I compared species presence and abundance in historical field notes to my own surveys and observations in 2017. Chapter 2 contains the results of this analysis of the broader Gulf intertidal community. Surveys at several historically sampled sites suggest that H. kubiniji has recovered from the 1978 mass-mortality event at some sites on the Baja California peninsula. At other locations H. kubiniji has not recovered. Interviews suggest that the species is well known to locals and is rarely collected for sale commercially as a curio. Even infrequent collection events might slow the recovery of this species. Additionally, it might be more difficult for H. kubiniji populations to recover in some areas due to abiotic factors like exposure to cold temperatures during extreme winter low tides. A comparison of historical field notes and 2017 surveys suggest that many species that were historically recorded at sites in the Northern and Central regions of the Gulf remain present. Although historical observations were sporadic and were not comprehensive, these data suggest that several species have declined at sites within the Gulf. The abundance of the Murcid gastropod Hexaplex nigritus might have decreased at sites in the Northern Gulf. For most species there was no evidence of change in the species distribution within the Gulf. However, several species of sea urchins were observed in 2017 outside their historical ranges. I present the 2017 presence and density of many Gulf intertidal species at sites for the first time. Hopefully this work will allow future researchers to accurately compare changes in the intertidal community of the Gulf.




sea star wasting, mass mortality, Heliaster kubiniji, Gulf of California, echinoderm, intertidal


Western Washington University

OCLC Number


Subject – LCSH

Marine invertebrates--Mortality--Mexico--California, Gulf of; Habitat surveys--Mexico--California, Gulf of

Geographic Coverage

Baja California (Mexico : State)




masters theses




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