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Simple Summary: Chitons are a charismatic group of mollusks that live underneath rocks on shores throughout the world, where they experience variations due to environmental factors. Temperature may cause animals to grow to a larger size in colder climates, a trend originally ascribed to endothermic animals. In this work, advanced techniques were used to describe both shape and size of chitons living under different temperature regimes on Pacific shores. The results show that chitons are larger in colder zones, as occurs in endothermic vertebrates. Respiration, reproduction and/or feeding strategies may explain this trend in chitons. Bergmann's rule relates the trend of increasing body size with higher latitudes, where colder climates are found. In the Mexican Pacific, three marine ecoregions are distinguishable across a latitudinal gradient. Stenoplax limaciformis is an abundant chiton species that is distributed on rocky shores in these ecoregions. Geometric morphometric analyses were performed to describe the shape and size variation of S. limaciformis between marine ecoregions that vary in sea surface temperature with latitude, thus testing Bergmann's rule. Individuals' body shape ranged from elongated to wide bodies. Although there was variation in chitons' body shape and size, the was no evidence of allometry among localities. The Gulf of California is the northernmost ecoregion evaluated in this work, where larger chitons were observed and lower sea surface temperature values were registered. The results suggest that S. limaciformis follows a trend to Bergmann's rule, such as endotherms. These mollusks do not need heat dissipation, but they do need to retain moisture. In addition, larger chitons were observed in zones with high primary productivity, suggesting that chitons do not delay their maturation due to food shortage. [ABSTRACT FROM AUTHOR]

Total mercury ([THg]) and selenium ([TSe]) concentrations were determined in California sea lion (Zalophus californianus) lanugo from the Gulf of California in 2021 and 2022. Relationships with sex, morphometrics, and year were evaluated. Following toxicological thresholds of concern for piscivorous mammals, most pups had a [THg] < 10 ppm, one pup (2021) had a [THg] > 20 ppm, no pups had a [THg] > 30 ppm. Females had significantly higher [TSe] than males; sex did not influence [THg]. [THg] and [TSe] in 2022 were significantly higher in the general population and male cohorts compared to 2021. Significant negative correlations were observed between [THg], [TSe], and morphometrics (2021). These results indicate that, compared to other pinniped species, regional California sea lions may have a decreased likelihood of experiencing Hg-related adverse health effects. Year-related changes in element concentrations suggest continued monitoring of this population to assess pinniped, environmental, and potentially, human health. • [THg] and [TSe] were determined in California sea lion lanugo. • Females had higher [TSe] than males; sex did not influence [THg]. • [THg] and [TSe] in 2022 were higher in general and male cohorts than in 2021. • California sea lions may have a low likelihood of Hg-related adverse effects. [ABSTRACT FROM AUTHOR]

Microplastics (MPs, < 5 mm in size) are highly bioavailable to many taxa within the marine ecosystem, either ingested directly or indirectly through trophic transfer from polluted prey. The ingestion analysis of these MPs from top predators, such as pinnipeds in Mexico, is relatively unexplored. Forty-eight scats from California sea lions were collected on six rookeries along the Gulf of California. From these scat samples, 294 suspected MPs particles were classified and chemically analyzed; 34% were synthetic and semi-synthetic, and 66% were non-synthetic. Blue-colored polyethylene terephthalate fibers were the most common type of MP registered. During laboratory work, multiple contamination control measures were implemented. Although the ingestion pathway is still unknown, our results support the other authors that suggest the potential trophic transfer of MPs to top predators and incidental ingestion while foraging. The particles documented here provide important baseline information for future MP research in the Gulf of California. [Display omitted] • 294 suspected microplastic particles were classified and chemically analyzed. • 34 % of particles analyzed were of synthetic and semi-synthetic origin. • Blue-colored PET fibers were the most common type of microplastic registered. • Our results infer that California sea lions are exposed to microplastics. [ABSTRACT FROM AUTHOR]

Supralittoral and high intertidal coastal zones are exposed to pollution from both marine and terrestrial sources and undergo higher deposition rates than the subtidal zone. It is therefore important to identify organisms for this section of the coastal area that can be tolerant to contaminants. The aim of this study was to determine if supralittoral isopods of the genus Ligia can be used as biomonitors, since they are abundant and widely distributed. For this purpose, concentrations of trace elements were determined in Ligia isopods in toto from 26 locations across the Gulf of California and Pacific coast of the Baja California peninsula, which were collected during the summers of 2009 and 2010. The concentrations of trace elements followed the order of; Zn≥Cu>As>Cd>Pb>Hg. Elevated concentrations of copper (up to 1010 μg/g) were detected in Ligia from Santa Rosalía (SRo), a locality where industrial mining of copper has historically occurred. Industrial and municipal sewage discharges appear to have contributed to the high concentrations of zinc (326 μg/g) and lead (144 μg/g) found in organisms from Guaymas location. The high mercury concentration in organisms from Mazatlán (M) (2.01 μg/g) was associated with a thermoelectric plant. Natural sources of metals were also detected; coastal upwelling appears to be associated with high cadmium concentrations in Ligia from Punta Baja (PB) (256 μg/g) in the Pacific coast, whereas hydrothermal vents may have contributed to high concentrations of arsenic at Ensenada (E) (61 μg/g). Our results suggest that Ligia isopods reflect the natural and anthropogenic inputs of trace metals in the environment and could potentially be used as biomonitor organisms of the intertidal rocky shores of the Gulf of California and Pacific coast. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the effects of fuel subsidies and value added tax refunds on the operation of two types of firms associated with the jumbo squid (Dosidicus gigas) fishery in Mexico: (a) firms with ships that catch shrimp and squid in different periods of the year and (b) firms that deploy outboard-motor boats to catch squid year-round. The cost-benefit ratios of the policies are analyzed for 2008–2015, both with and without subsidy-related income. Additionally, the net cash surplus is calculated. The elimination of subsidies may affect jobs related to vessel operations in the squid fishery and may also encourage the voluntary retirement of shrimp ships. This effect is less evident in the case of the smaller boats. Strategies aimed at improving the landed squid prices are nonetheless suggested. [Copyright &y& Elsevier]

Abstract: The environmental changes due to the Colorado River damming, have affected the ecological functioning of the nursery river delta and consequently the population of fishermen that live of the natural marine resources of the upper Gulf of California. We propose the use of urban wastewaters as a source of nutrients to fertilize the estuary, increase the primary productivity and therefore increase the population size of the estuarine dependent species, which are important for the fisheries in the region. In this way, we could partially restore the delta's ecological functioning and thus solve environmental, social, and economic problems. With a wastewater flow of 800 l·s-1 from “Las Arenitas” treatment plant, we could increase the primary organic productivity and ~1000 metric tons (mT) of shrimp landings of the region. These calculations are just for one fishery, but in a magnitude that could also increase in others. [Copyright &y& Elsevier]

Pocillopora verrucosa is a branching, reef-building coral, and a simultaneous hermaphrodite that reproduces sexually and asexually by fragmentation. In the Gulf of California, local P. verrucosa populations have mixed modes of reproduction which vary in frequency by site. Sexual and asexual reproductions were assessed using multi-locus genotypes deriving from six microsatellite loci at every location. Clone frequencies varied from 0.30 at Loreto to 0.96 in the San Lorenzo Channel. Isla Espíritu Santo and the San Lorenzo Channel were mostly asexual subpopulations, presented the lowest genotypic richness ( N/ N = 0.1-0.12) and genotypic diversity ( G/ G = 0.04), and were dominated by one or two multi-loci genotypes ( G/ N = 0.35-0.45). Loreto, El Portugués, and Cabo Pulmo were mostly sexual with high Ng/ N (0.80-0.74) and G/ G (0.52-0.58) and did not show domination by a single multi-locus genotype ( G/ N = 0.70-0.74). There was a significant relationship ( P < 0.05) between tropical storm frequency and the genotypic indexes of richness and diversity modeling an inverted U-shape, which indicates that the sites where storm frequencies were the highest had mostly clonal populations; sites exposed to intermediate or low storm frequencies had mostly sexual populations. The study included a restored area (San Lorenzo Channel) where genotypic analyses showed a high level of clonality similar to natural conditions occurring in a nearby subpopulation (Isla Espíritu Santo), which demonstrates the low natural genetic diversity of the area. This study showed that a species with mixed reproduction modes has different maintenance strategies at a regional and even local level among populations indicating the crucial role that storms play in population structure. [ABSTRACT FROM AUTHOR]

The purpose of this work was to use the deep-water chimaera Hydrolagus colliei to examine the bioaccumulation and availability of Hg and Se in its deep-water habitat; the Se:Hg molar ratio was calculated to establish baseline information of the species and its associated ecosystem. The organisms were collected from northern Gulf of California. Hg levels in muscle were higher than liver and the opposite pattern happened with Se concentrations. Female had total lengths and weights higher than male but there were not found differences between elements concentrations by sex. Hg in muscle was correlated with weight. Molar Se:Hg ratio in muscle was the lowest compared to the liver. It was hypothesized that Hg and Se uptake to H. colliei were by its feeding habits because is a dominant species component of the demersal ecosystem and that play and important functional role in the control of oceanic ecosystem structure and function. • Hg and Se were measured in muscle and liver of the chimaera Hydrolagus colliei. • Hg range in muscle was 0.05–0.55 mg kg−1 and in liver 0.03–1.24 mg kg−1. • Se ranged up to 5.5 mg kg−1 in liver and in muscle from 0.14 to 1.23 mg kg−1. • The lower Se:Hg molar ratio was in muscle (1.30) and the highest in liver (68.6). • It was assumed that Hg and Se uptake of H. colliei were by its feeding habits. [ABSTRACT FROM AUTHOR]

Population growth around water bodies is deteriorating environmental quality. The benthic foraminiferal and trace element concentration in a pair of short sediment cores were used to establish the quality of the sedimentary environment in a tropical coastal lagoon in the southwestern Gulf of California. From 25 cm depth towards the surface of the sediment core, Ammonia beccarii was dominant over nontolerant species and the concentrations of V, Ni, Co, Zn, Cu, Hg and Pb in the sediments increased compared with the lower depth intervals. This finding suggests a deterioration in the environmental quality of the lagoon since 1980, associated with an increase in the sizes of the population and vehicle fleet in the city of La Paz, Baja California Sur, and with the operation of three fossil fuel-based thermoelectric plants since 1985. • Ammonia beccarii was dominant over nontolerant species in sediment core. • V, Ni, Co, Zn and Cu concentrations increased between 6% and 19% in sediment core. • Deterioration in the environmental quality of the lagoon since 1980. • FSI suggest poor to extremely poor environment in the interior of the lagoon. [ABSTRACT FROM AUTHOR]

Concentrations of Potentially Toxic Elements (PTEs) were determined in sediments from Santa María La Reforma (SAMARE) coastal lagoon and Mocorito River, Mexico. Furthermore, biochemical composition of organic matter in sediments was analyzed to assess their trophic status. The PTEs concentrations followed the order Fe > Pb ∼ Zn > Cr ∼ Cu > Ni ∼ As ∼ Co > Cd. Except for As, PTEs showed correlation between them indicating a common source. As and Pb were above the threshold levels of toxic effect, but they did not exceed the levels of probable effect for biota. Metals were correlated with carbohydrates and As with lipids. Low protein/carbohydrate ratios suggest that decomposed detritus of nitrogen-rich algae as well as fresh mangrove litter can be present. These biochemical proxies suggest that meso-oligotrophic conditions prevail in SAMARE. Considering that fishing activities are practiced and that the northern portion of SAMARE was classified as a RAMSAR site, the information presented is useful to generate strategies for the management of this ecosystem. • Except for As, the PTEs showed correlation among them indicating a common source. • Arsenic and Pb concentrations were above the threshold levels of toxic effect. • The PTEs were correlated with carbohydrates main component of labile organic matter. • Low PRT/CHO ratios suggest a mixture of nitrogen-rich algae and mangrove residues. • These biochemical proxies suggest that meso-oligotrophic conditions prevail in SAMARE. [ABSTRACT FROM AUTHOR]