Fishes of the Cabo Pulmo reef, Gulf of California, Mexico: systematic list and aspects of abundance and biogeography

The Cabo Pulmo reef is the most important coral formation of the Gulf of California; however, its ichthyological fauna has been poorly studied. To produce a systematic list with data on relative abundance and frequency, and biogeographical affinities, we relied on visual census, field observations, analysis of commercial and sport fisheries (from 1986 to 1998), and the literature. A total of 236 species have been recorded at Cabo Pulmo (155 genera and 60 families). This number doubles previous compilations and represents 65.1% of all reef fishes known from the Gulf of California, and about 35% of its entire shallow-water fishes. Of the total species number, 68.3% are from the Panamic Province, 11.0% Indo Pacific colonizers and the same percentage gulf endemics, 7.6% are circumtropical, 1.7% Atlantic and 0.5% cosmopolitan; none are endemic to the reef. The most abundant taxa are the labrids Thalassoma lucasanum, T. grammaticum and the pomacentrid Chromis atrilobata. Only eleven species (4.7% of total) appeared in 75% to 100% of census, and 36 (15.3% of total) had high levels of both abundance and frequency, evidencing that the community is dominated by few taxa. Local species richness exceeds the number reported for most rocky or coral reefs of the Pacific coast of México, and indicates that Cabo Pulmo is a key area in the gulf and the entire Mexican Pacific, from the ichthyological point of view.     

Issues of ecosystem-based management of forage fisheries in “open” non-stationary ecosystems: the example of the sardine fishery in the Gulf of California

The Gulf of California system presents major challenges to the still developing frameworks for ecosystem-based management (EBM). It is very much an open system and is intermittently subject to important influxes of migratory visitors, including large pelagic predatory fishes and small pelagic forage fishes. These migrants include the more tropical species from the coastal ecosystems to the south and perhaps subtropical sardines and anchovies from the California Current upwelling system. In addition to the multi-annual ENSO-scale and what may seem to be rather erratic episodes of major population incursions, the Gulf presents nonstationary, transient aspects on a variety of longer time scales. Moreover, the removal of top predators by commercial and sport fisheries has introduced trends that must be affecting the entire ecosystem, and certainly the forage fishes that are their major prey base. In addition to size limits, fishing seasons, area closures and license limitations, the fishery is managed by an ad hoc adaptive management system, in which the fishing season can be shortened or additional areas closed to fishing if pre-season exploratory fishing surveys indicate a shortage of small pelagic fishes on the fishing grounds. Whether this system is likely to be sustainable in the long term is difficult to determine, given the potential for rapid changes in the system because of environmental changes and/or feedbacks within the food web. Thus it appears that innovative management frameworks, among other things utilizing the comparative method, may be required in order to determine defensible tradeoffs between precaution and resource utilization.     

PHYLOGEOGRAPHY OF THE SPOTTED SAND BASS, PARALABRAX MACULATOFASCIATUS: DIVERGENCE OF GULF OF CALIFORNIA AND PACIFIC COAST POPULATIONS

Abstract Have the warm tropical waters and currents of the southern Gulf of California, Mexico (also known as the Sea of Cortez), formed a barrier to gene flow, resulting in disjunct populations in the upper gulf that are isolated from the outer Pacific Coast? Phylogeographic and genetic divergences of the spotted sand bass, Paralabrax maculatofasciatus, from three Gulf of California and two outer Pacific coastal locations were tested using mitochondrial DNA (mtDNA) control region sequences. Sequence data from two congeners that are sympatrically distributed along the outer Pacific Coast, the barred sand bass, P. nebulifer, and the kelp bass, P. clathratus, were used to gauge the levels of genetic divergences. Differences among the three species and between the northern gulf and outer Pacific coastal populations of P. maculatofasciatus also were analyzed using 40 allozymic presumptive gene loci. Allozyme and mtDNA analyses each revealed many fixed differences among the species. Three significant allozymic frequency differences and two fixed mtDNA substitutions differentiated the gulf and outer Pacific coastal populations of P. maculatofasciatus. Three unique mtDNA haplotypes and three unique allozyme alleles were identified from the outer Pacific coastal population. The gulf sites contained four unique mtDNA haplotypes and six unique allozyme alleles. Partitioning of the mtDNA variation revealed that 72% of the variance occurred between the gulf and outer Pacific Coast, 20% between sampling sites in the two regions, and 8% within the sites. There appears to be little gene flow across the waters of the southern Baja Penninsula, producing divergence estimated as 120,000 to 600,000 years between the outer Pacific coastal and the Gulf of California populations. This separation level may date to a hypothesized seaway closure near La Paz, Mexico, during the mid‐Pleistocene, and characterizes other fish populations. A second pattern of deeper allopatric species‐level divergences in some other fishes may date to a Pliocene closure of a mid‐Baja Penninsular seaway. Significant differences also were discerned in P. maculatofasciatus between the San Diego and central Baja California coastal sites and between the upper/central and the lower gulf locations. Variation between locations in the two regions may be indicative of larval retention and low adult migration, which needs to be tested further.     

Rocky intertidal fish communities of California: temporal and spatial variation

Synopsis We examined data from our own and published collections of intertidal and shallow littoral fishes of the North American Pacific Coast with respect to temporal and spatial trends in species composition and dominance. We compared (1) recent and past intertidal collections made five and seven years apart, respectively, for two California localities, (2) intertidal collections from twelve localities in California, Oregon, and British Columbia, and (3) intertidal versus subtidal collections at one California locality. Temporal comparisons indicated substantially lower abundance of the cottid Oligocottus snyderi at two California localities during 1984, at one locality due to depressed abundance of young. Interannual differences in abundances suggested that other tidepool fish assemblages undergo significant changes as well. Geographical comparisons indicated general similarity in species composition, with cottids predominating in tidepools although several other families also were well represented (e.g., Stichaeidae, Scorpaenidae). Eel-shaped stichaeids and pholids occurred at high densities in exposed boulder fields. Both the tidepool and boulder field assemblages showed north-south changes in species abundances. Comparison of collections from the intertidal and subtidal zones at one California locality demonstrated that fishes of these habitats form two essentially distinct assemblages, with most species restricted to or concentrated in one or the other habitat.     

Ichthyofauna of the Navidad Bay, Jalisco, México]

A check-list and the relative abundance of the ichthyofauna from Bahia de Navidad, Jalisco, Mexico is presented. This poorly known area of the eastern Tropical Pacific ocean is characterized by its great fish diversity. A total of 245 fish species (163 genera, 72 families) were collected during the 1994-1995 annual cycle. Vouchers were deposited in Centro de Ecologia Costera, Universidad de Guadalajara. The most important families in number of species were Carangidae (20 species), Haemulidae (20), Serranidae (17), Sciaenidae (13) and Lutjanidae (8); 20 species represented 85% and 80% of relative abundance and biomass respectively. Microlepidotus brevipinnis, Caranx caninus, Caranx caballus, Kiphosus analogus and Caranx sexfasciatus, were the dominant species. Most fish species collected in Bahia de Navidad have zoogeographical affinity with the Panamic Province (65%), and in lesser proportion with the Eastern Pacific Ocean (19%), Circumtropical (7%), Mexican Province (5%), Indo-Pacific Ocean (3%) and Gulf of California (0.4%). The great ichthyological affinity between the study area and the southern Gulf of California suggests an extension of the of Gulf southern limit.     

Population genetic structure of annual and perennial populations of Zostera marina L. along the Pacific coast of Baja California and the Gulf of California

The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using θ_ST values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest θ_ST (0.13–0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (θ_ST = 0.04–0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast.     

Comparative ecology of subtidal actiniarians from the coasts of California and the Gulf of Maine,USA

Shallow subtidal populations of sea anemones occupying hard substrates along the California (Pacific) and Gulf of Maine (Atlantic) coasts of the USA are compared. The diversity of anemones in the southern Gulf of Maine to 35 m is low (4 species) in contrast to similar habitats in California (at least 11 species), but parallel patterns of individual size, distribution and predation impacts occur. Water motion influences depth distribution and size, while predation affects size, population structure and habitat selection. The nudibranch Aeolidia papillosa exerts a similar pressure on population structure in some anemone species in both areas as a size selective predator. The seastar Dermasterias imbricata appears to magnify the selective pressure for large size in the eastern Pacific coastal zone. Interspecific aggression of anemones determines some distribution patterns in areas of overlap.     

Análisis de la distribución geográfica de los anomuros (Crustacea: Decapoda) del Golfo de California,México

The anomuran crabs are important from the biogeographic perspective because of their benthonic behavior in their adult state. For this reason, the present work summarizes the different studies developed to date on these crustaceans within the Gulf of California and reinforces the separation of the zone from others in the Province of Cortéz, or Cortesiana. The Gulf of California is inhibited by seventy-eight species of anomurans, belonging to seven families and twenty-eight genera. The best represented family regarding the number of genera (eleven), species (forty-five) and endemic species (eleven) is the Porcellanidae, followed by the Diogenidae with eight genera, fifteen species and four endemic species. The Gulf of California species are distributed in three large zoogeographical groups in the Eastern Pacific, the main one being the Panamic with an intrusion to the Gulf of 69.23% of the species reported. A second important group is that of the endemic species of the Gulf, with 24.35% of the existing species. The boreal species group with intrusion to the Gulf is present with 6.41%. Within the Californian Gulf, ten different zoogeographical groups are found, which demonstrate the great complexity of anomuran distribution, a product of the evolutionary history of this interior sea.     

MHC gene configuration variation in geographically disparate populations of California sea lions (Zalophus californianus)

Major histocompatibility complex (MHC) class II DRB genotypes were examined in two geographically isolated populations of California sea lions (Zalophus californianus) (Gulf of California and California coastal Pacific Ocean). Genomic DNA from 227 California sea lions was examined using eight sequence-specific primer (SSP) pairs flanking the putative peptide-binding site. A total of 40 different Zaca-DRB genotype configurations were identified among the 227 individuals. Using SSP-PCR, significant differences were found between coastal California and Gulf of California Zalophus populations in numbers of DRB sequences per individual and configuration of sequences within individuals. Additionally, unique local patterns of MHC diversity were identified among the Midriff Island animals. These population differences are consistent with either ecologically distinct patterns of selection pressures and/or geographical isolation. The consequences of these partitioned MHC configurations at the population level are as yet unknown; however, the worldwide increase in emerging marine diseases lends urgency to their examination.     

Vicariance and dispersal across Baja California in disjunct marine fish populations

Abstract.— Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study.     

Multinational Tagging Efforts Illustrate Regional Scale of Distribution and Threats for East Pacific Green Turtles (Chelonia mydas agassizii)

To further describe movement patterns and distribution of East Pacific green turtles (Chelonia mydas agassizii) and to determine threat levels for this species within the Eastern Pacific. In order to do this we combined published data from existing flipper tagging and early satellite tracking studies with data from an additional 12 satellite tracked green turtles (1996-2006). Three of these were tracked from their foraging grounds in the Gulf of California along the east coast of the Baja California peninsula to their breeding grounds in Michoacán (1337-2928 km). In addition, three post-nesting females were satellite tracked from Colola beach, Michoacán to their foraging grounds in southern Mexico and Central America (941.3-3020 km). A further six turtles were tracked in the Gulf of California within their foraging grounds giving insights into the scale of ranging behaviour. Turtles undertaking long-distance migrations showed a tendency to follow the coastline. Turtles tracked within foraging grounds showed that foraging individuals typically ranged up to 691.6 km (maximum) from release site location. Additionally, we carried out threat analysis (using the cumulative global human impact in the Eastern Pacific) clustering pre-existing satellite tracking studies from Galapagos, Costa Rica, and data obtained from this study; this indicated that turtles foraging and nesting in Central American waters are subject to the highest anthropogenic impact. Considering that turtles from all three rookeries were found to migrate towards Central America, it is highly important to implement conservation plans in Central American coastal areas to ensure the survival of the remaining green turtles in the Eastern Pacific. Finally, by combining satellite tracking data from this and previous studies, and data of tag returns we created the best available distributional patterns for this particular sea turtle species, which emphasized that conservation measures in key areas may have positive consequences on a regional scale.     

Habitat suitability of Rhincodon typus in three localities of the Gulf of California: Environmental drivers of seasonal aggregations

The whale shark is an endangered species that usually feeds in coastal areas of highly productive seas such as the Gulf of California, Mexico. This study aims to describe the effect of sea surface temperature, chlorophyll a, bathymetry and slope on the habitat suitability of whale sharks in three important aggregation sites of the Gulf of California. A total of 2396 records of occurrence of whale sharks were obtained from international databases and scientific literature between 1996 and 2018. These records were used for the creation of a species distribution model using MaxEnt for each of the three aggregation sites. The concentration of chlorophyll a explained 71% of the habitat suitability, followed by bathymetry and slope with a combined 17%, and sea surface temperature constituting 10% of the model. Habitat suitability was related to areas where nontargeted fisheries may impact whale sharks through bycatch, entanglement and ship strikes. The implications for the conservation of whale sharks should be considered for management decisions in terms of marine protected areas, fishing refugees or bans, and other regulations regarding fisheries activities.     

Species of the planktonic diatom genus Pseudo-nitzschia of the Pacific coasts of Mexico

Species of the diatom genus Pseudo-nitzschia are common in the marine phytoplankton world-wide. Some species of this genus have been proved to be source of domoic acid (DA), a powerful toxin causing Amnesic Shellfish Poisoning (ASP) in humans and probably mass mortality in sea birds and mammals. Net plankton samples obtained during several cruises and seasons from the Pacific coasts of Mexico: western coasts of Baja California, Gulf of California, coasts of the tropical Pacific of Mexico (including the Gulf of Tehuantepec), were analyzed to study the species of the diatom genus Pseudo-nitzschia. Four species ( P. australis, a presumed toxic species, P. fraudulenta, P. lineola, P. pungens) and one former species of the genus, Nitzschia americana were recorded and studied by light and electron microscopy. The most common species was P. pungens, widely distributed along the Pacific coasts of Mexico. All other species appeared occasionally and in low relative abundances. The probable misidentification of P. australis as P. seriata is discussed, as well as the presence of another potentially toxic species, P. delicatissima, in the Gulf of California. No case of toxicity (ASP) has been fully documented and therefore related to toxic Pseudo-nitzschia species in the Gulf of California. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial distribution of sharks captures in the Pacific of Nicaragua and its relationship with several oceanographic variables

Between August 1995 and August 1997 long line fishing techniques and a bathythermograph were used to correlate some physical variables with the spatial distribution of four shark species in 26 fishing cruises off the Nicaraguan Pacific Coast. They were the thresher (Alopias vulpinus), blue (Prionace glaucea), gray (Carcharhinus falciformis) and hammer (Sphyra lewini). All species concentrated in the southeastern Nicaraguan Pacific, at the seasonal upwelling area of Papagayo Gulf. The range of sea surface temperatures in which the sharks were captured was 25-28 degrees C. We could clearly associate this physical parameter with shark availability. The vertical distribution of the captured sharks suggests that they occupy termocline levels above the 15 degrees C isotherm. Although these species are oceanic, the blue shark was captured in ocean waters over the 1800 m isobar, while the grey and thresher sharks where close to the continental shelf. Body length in decreasing order are: thresher (210-290 cm, SN = 21), blue (60-240 cm, SN = 13) and gray (80-200 cm, SN = 17).     

INTRASPECIFIC GENETIC DIFFERENTIATION IN CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS) FROM SOUTHERN CALIFORNIA AND THE GULF OF CALIFORNIA

Intraspecific patterns of mitochondrial DNA sequence variation were determined among California sea lions ( Zalophus califomianus californianus ) from three colonies along the Pacific coast of southern and Baja California and one colony in the Gulf of California. We found no variation in 368 base pairs (bp) of cytochrome b sequence among 40 sea lions from these localities, but analysis of 360 base pairs of control region revealed eleven genotypes. The four genotypes found in the Gulf of California population were unique and phylogenetically distinct from those found in sea lions along the Pacific coast. The average sequence divergence between Gulf and Southern California genotypes was 4.3%, suggesting a relatively long period of isolation. However, colonies along the Pacific coast, which are less than 200 km apart, shared mtDNA genotypes, indicating that recent genetic exchange has occurred between them. Therefore, we suggest that regional female philopatry exists in California sea lions. Regional boundaries may be related to oceanic currents or patchiness in the distribution of resources. Further research is needed to better understand the underlying causes of genetic differentiation in the California sea lion.     

A seasonal analysis of the nutritional condition of deep-sea macrourid fishes in the north-east Pacific

Of three common macrourids Coryphaenoides armatus and Coryphaenoides yaquinae were collected from 1995 to 1998 at an abyssal station, c . 220 km west of Point Conception, California in the north-east Pacific (4100 m depth). Coryphaenoides acrolepis was collected from 1997 to 1998 in the San Diego Trough (1200 m depth). Energy storage in all three species was primarily in the liver, which was up to 56% lipid (wet mass) and up to 96% triglyceride. No seasonal variation in nutritional condition was found for C. armatus or C. yaquinae . There was, however, a significant increase in muscle water content and liver lipid content and a significant decline in muscle lactate dehydrogenase activity for C. armatus between 1996 and 1998. Potential mechanisms for these interannual shifts are proposed. No seasonal variation in parameters was found for C. acrolepis but a small seasonal periodicity in feeding activity may have existed. The seasonal deposition of phytodetritus in the deep sea is of little or no consequence to these fishes.     

A catalogue of skulls and jaws of eastern tropical Pacific blennioid fishes (Blennioidei: Teleostei): A proposed evolutionary sequence of morphological change

Skulls and jaws are compared in 35 species of tropical eastern Pacific (mainly Gulf of California) blennioid fishes (5 species of Tripterygiidae, 13 Labrisomidae, 12 Chaenopsidae, 5 Blenniidae). Morphotypes are arranged in a series from relatively large-mouthed fishes (tripterygiids and a few labrisomids) with protrusible jaws and conical teeth to species with small, non-protrusible jaws and a single row of incisiform teeth. This polarity of arrangement probably reflects the direction of phylogenetic development, as suggested by outgroup comparison with other perciform fishes. Distribution patterns of morphotypes in a simple morphospace, obtained by combining dentition, shape of the jaw arch and jaw protrusibility, are discussed within an adaptive context.     

Phylogeographic patterns of a lower intertidal isopod in the Gulf of California and the Caribbean and comparison with other intertidal isopods

A growing body of knowledge on the diversity and evolution of intertidal isopods across different regions worldwide has enhanced our understanding on biological diversification at the poorly studied, yet vast, sea–land interface. High genetic divergences among numerous allopatric lineages have been identified within presumed single broadly distributed species. Excirolana mayana is an intertidal isopod that is commonly found in sandy beaches throughout the Gulf of California. Its distribution in the Pacific extends from this basin to Colombia and in the Atlantic from Florida to Venezuela. Despite its broad distribution and ecological importance, its evolutionary history has been largely neglected. Herein, we examined phylogeographic patterns of E. mayana in the Gulf of California and the Caribbean, based on maximum‐likelihood and Bayesian phylogenetic analyses of DNA sequences from four mitochondrial genes (16S rDNA, 12S rDNA, cytochrome oxidase I gene, and cytochrome b gene). We compared the phylogeographic patterns of E. mayana with those of the coastal isopods Ligia and Excirolana braziliensis (Gulf of California and Caribbean) and Tylos (Gulf of California). We found highly divergent lineages in both, the Gulf of California and Caribbean, suggesting the presence of multiple species. We identified two instances of Atlantic–Pacific divergences. Some geographical structuring among the major clades found in the Caribbean is observed. Haplotypes from the Gulf of California form a monophyletic group sister to a lineage found in Venezuela. Phylogeographic patterns of E. mayana in the Gulf of California differ from those observed in Ligia and Tylos in this region. Nonetheless, several clades of E. mayana have similar distributions to clades of these two other isopod taxa. The high levels of cryptic diversity detected in E. mayana also pose challenges for the conservation of this isopod and its fragile environment, the sandy shores.     

Biogeographical patterns of rocky intertidal communities along the Pacific coast of North America

Aim Our aim in this paper is to present the first broad‐scale quantification of species abundance for rocky intertidal communities along the Pacific coast of North America. Here we examine the community‐level marine biogeographical patterns in the context of formerly described biogeographical regions, and we evaluate the combined effects of geographical distance and environmental conditions on patterns of species similarity across this region. Location Pacific coast of North America. Methods Data on the percentage cover of benthic marine organisms were collected at 67 rocky intertidal sites from south‐eastern Alaska, USA, to central Baja California Sur, Mexico. Cluster analysis and non‐metric multidimensional scaling were used to evaluate the spatial patterns of species similarity among sites relative to those of previously defined biogeographical regions. Matrices of similarity in species composition among all sites were computed and analysed with respect to geographical distance and long‐term mean sea surface temperature (SST) as a measure of environmental conditions. Results We found a high degree of spatial structure in the similarity of intertidal communities along the coast. Cluster analysis identified 13 major community structure ‘groups’. Although breaks between clusters of sites generally occurred at major biogeographical boundaries, some of the larger biogeographical regions contained several clusters of sites that did not group according to spatial position or identifiable coastal features. Additionally, there were several outliers – sites that grouped alone or with sites outside their region – for which localized features may play an important role in driving community structure. Patterns of species similarity at the large scale were highly correlated with geographical distance among sites and with SST. Importantly, we found community similarity to be highly correlated with long‐term mean SST while controlling for the effects of geographical distance. Main conclusions These findings reveal a high degree of spatial structure in the similarity of rocky intertidal communities of the north‐east Pacific, and are generally consistent with those of previously described biogeographical regions, with some notable differences. Breaks in similarity among clusters are generally coincident with known biogeographical and oceanographic discontinuities. The strong correlations between species similarity and both geographical position and SST suggest that both geography and oceanographic conditions have a large influence on patterns of intertidal community structure along the Pacific coast of North America.