Infections of Northern Anchovies (Engraulis mordax) with the parasitic copepod Caligus klawei are reported from inspection of 1,256 anchovies collected at Inner Cabrillo Beach, San Pedro, CA during multiple collecting trips from 2014-2016. The overall prevalence of infection across all samples was 31.6%. The overall intensity of infection was 1.19. No significant correlation between the standard length of the host and prevalence or intensity was observed. Thirty-five of the 556 copepod specimens collected were in a chalimus developmental stage. This study constitutes the first record of developmental stages of C. klawei and their infection of E. mordax, the only recorded host for this species of copepod. Prior to this study, it was hypothesized that a possible intermediate host other than E. mordax may exist for the developmental stages of C. klawei. This current observation weakens the previous theory of an intermediate host and provides strong support that E. mordax is the sole host of C. klawei throughout its life cycle. A description of the male is also given herein for the first time, based on specimens collected, with a comparison of sexually dimorphic features.

Members of the monofamilial chondrichthyan order Squatiniformes, commonly known as angel sharks, sand devils, ange de mer, and angelotes, are primarily benthic dwelling sharks found mainly in temperate and sub-tropical parts of the Atlantic and Pacific Oceans. Squatiniformes are very easily recognized from other shark-like fishes, but the individual species within the order are much more difficult to distinguish from each other. In the eastern North Pacific (ENP) region, three species descriptions were published from 1859 to 1913. Since the latter date, the systematics of the entire order of Squatiniformes has been in a state of flux, from having only one description recognized as valid to having all three being recognized as valid at different points in history. Currently only two descriptions are considered valid Squatina californica, Ayers, 1859 and Squatina armata (Philippi, 1887). Herein, the presence of at least four phenotypic morphs in the ENP is confirmed and a revised dichotomous key for the Squatiniformes of the region is presented. Additionally, numerous mistakes in the classification and cataloging of museum specimens are noted and corrected.

Parasitism is one the most common lifestyles on earth. Parasites are important components of virtually all ecological communities and parasite research can help to elucidate many aspects of the ecology of their hosts. This dissertation focused on studying the metazoan parasites of the California grunion, Leuresthes tenuis and other fish hosts in the family Atherinopsidae. In Chapter 1, the metazoan parasites of L. tenuis were investigated at five localities in southern California. A total of 2,902 parasites belonging to 26 taxa were recovered from 900 specimens of L. tenuis collected between 2016 and 2018. Comparisons of parasite communities showed that the parasite fauna of L. tenuis varied among localities. This variation suggests that L. tenuis may stay relatively close to their spawning grounds throughout their lives. In Chapter 2, a redescription is provided of the parasitic copepod Caligus olsoni, associated with L. tenuis and other fishes in the northeast Pacific. Caligus olsoni was morphologically compared to another species, Caligus serratus. In light of the morphological similarities observed between these two species, we propose to treat C. serratus as a junior subjective synonym of C. olsoni. Based on previous reports, C. olsoni appeared to be highly host-specific. However, with the proposed synonymy of C. olsoni and C. serratus, C. olsoni has, in fact, low host specificity, with 16 fish host species currently reported from 12 families. In Chapter 3, the parasite communities of L. tenuis and three other host species in the family Atherinopsidae were compared. A total of 5,677 parasites from 25 taxa were recovered from the four host species. The results showed significant differences in parasite communities in relation to host species. The three most abundant parasite taxa found in this study, which combined accounted for more than 78% of the total number of parasites recovered, were associated with two of the host species. Differences in parasite communities may be explained by variations in diet and feeding strategies among the hosts species investigated.

Exploitation of sharks by both commercial and recreational fisheries has caused decreasing numbers resulting in population collapses. Sharks are extremely vulnerable to the effects of exploitation due to life-history characteristics including long lifespans, low fecundities, and late maturities. One family of shark, the Triakidae, has been the subject of global exploitation for greater than 80 years, especially within the eastern Pacific. The Triakidae is a primary component of the eastern Pacific elasmobranch assemblage considered both commercially and recreationally important with several endemic species found within the region including Mustelus albipinnis, M. californicus, M. dorsalis, M. henlei, M. lunulatus, and Triakis semifasciata. In regards to conservation efforts, there is a general paucity of information regarding the status of triakid sharks. As a result of this paucity of information, this study used mitochondrial and nuclear genetic markers to investigate: 1) gene flow among globally distributed populations of the tope shark, Galeorhinus galeus; 2) determine the existence of multiple paternity in M. henlei from within the northern portion of the species' range; and, 3) explore the population connectivity of M. henlei among localities distributed throughout the range of the species from along the northeastern Pacific coast.

A lack of gene flow among globally distributed populations of the tope shark, G. galeus from North America, South America, Western Europe, South Africa, and Australia has been observed based on data from thirteen species-specific microsatellite loci. These data support previous patterns of gene flow based on mitochondrial control region sequence data and indicate the isolated nature of globally distributed populations of G. galeus. As a result, these populations should be managed separately and the currently recognized species status of G. galeus as monotypic should be reconsidered.

The existence of polyandry and multiple paternity within a population of M. henlei at Santa Catalina Island, CA over a period of eight years has been confirmed based on data from 18 litters and four species-specific microsatellites. The observed range of multiple paternity, 0-40%, is significantly lower than that observed in another population of M. henlei from Baja California (93% of 14 litters were observed to be sired by multiple males within a single year). As population sizes differ between the two localities (Baja California > Santa Catalina Island), the rate at which females encounter mates may be responsible for the difference in the frequencies of multiple paternity observed between Santa Catalina Island and Baja California.

Data from six species-specific microsatellites and the mitochondrial control region have detected three distinct populations of M. henlei in the northeastern Pacific (Northern (San Francisco), Central (Santa Barbara, CA, Santa Catalina Island, CA, Punta Lobos, Baja California, Mexico, and San Felipe, Baja California, Mexico), and Southern (Costa Rica)). Reduced mitochondrial genetic diversity was observed in San Francisco and Santa Catalina relative to all other localities. Possible reasons for the observed reductions in genetic diversity may be the recent establishment of isolated populations after Pleistocene glaciations, female philopatry to nursery areas, or a combination of the two. Long-term gene flow was asymmetric among localities with the predominating pattern being from the north to the south. Gene flow within the past two to three generations appears to be virtually nonexistent among localities with the exception of Punta Lobos that demonstrated significant gene flow to all other localities within the central population. This pattern may be the result of changing climate and may reflect the dispersal of tropical M. henlei into subtropical and temperate regions.

Several species of fishes have been introduced into the Santa Clara River system in southern California, including Catostomus santaanae (Santa Ana sucker), Catostomus fumeiventris (Owens sucker), Gila orcutti (arroyo chub), and Pimephales promelas (fathead minnow). These species are known to inhabit similar ecological niches but little is known about their associated parasite fauna. Two C. fumeiventris, 35 C. santaanae, 63 hybrid catostomids, 214 G. orcutti, and 18 P. promelas were collected and necropsied in the summers of 2017 and 2018. Nine macroparasite taxa were harvested including seven native, and two nonnative parasites Schyzocotyle acheilognathi (Asian fish tapeworm) and Lernaea cyprinacea (anchor worm). Prevalence and intensity of parasites were not related to the genetic history of these catostomids. This is the first host-association record for G. orcutti with Gyrodactylus sp., S. acheilognathi, diplostomid metacercariae, Rhabdochona sp, Contracaecum sp., and larval acuariid cysts and for P. promelas with larval acuariid cysts.

The leatherback sea turtle (Dermochelys coriacea), a species considered vulnerable by the International Union for the Conservation of Nature, is found nesting on the island of Puerto Rico. In this study, nesting and hatching activity were analyzed for the first 17 years of collected data, 1992-2008, from El Balneario beach in the town of A�asco on the west coast of Puerto Rico. These data were obtained from Department of Natural and Environmental Resources (DNER), a strand of the government of Puerto Rico. The study data were separated into two bins of the first and last years (bin 1: 1992-1997, excluding 1996, and bin 2: 2004-2008). There were significantly more nesting events (i.e., act of a sea turtle burying its eggs) in bin 2 than in bin 1. However, significantly more eggs hatched and more sea turtles emerged from the nest to the sand in bin 1 than in bin 2. Nest disturbances (poaching, light pollution, and compacted sand) did not significantly affect the percentage of eggs that successfully hatched or emerged in a nest. The likelihood of a nest to have zero hatched eggs was higher in nesting areas disturbed by light pollution. Studies on the results of conservation efforts on sea turtle reproduction have not been conducted at many of the breeding locations in Puerto Rico. The conservation efforts by the government and community may have increased nesting events. The DNER worked on educating and involving the community in monitoring efforts by encouraging them to volunteer and become stewards of the sea turtles and the nesting beach. For example, at the beginning of the project the community would not report activities that were detrimental to sea turtles or hatching and nesting events. In contrast, during the last years of the study, the community was heavily involved in educating other community members, the monitoring of the beach for sea turtle activities and reporting negative anthropogenic factors that can impact sea turtles. Lower numbers in hatching and emergence success may be attributed to effects on egg development created by a potential increase in the presence of fungi (Fusarium solani) and bacteria (Serratia marcescens), as well as temperature and humidity in the nest clutch.