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Germination of cysts serves as inoculum for the proliferation of some dinoflagellates, and cyst abundance in sediments represents crucial information to understand and possibly predict Harmful Algae Blooms (HABs). Cyst distribution is related to the physical characteristics of the sediments and the hydrodynamics (circulation) of a particular region. In the northern Gulf of California (nGC) several Gymnodinium catenatum HABs have been recorded. However, the presence of resting cysts and the effect of hydrodynamics on their distribution in the nGC have not been investigated. This study evaluated cyst abundance, distribution and their relation to local circulation in surface sediments during two periods that coincided with a non-bloom year condition (July 2016) and after a major HAB registered in the nGC that occurred in January 2017. Also, a numerical ocean model was implemented to characterize the transport and relocation of cysts and sediments in the region. Gymnodinium catenatum cysts were heterogeneously distributed with some areas of high accumulation (as high as 158 cyst g−1, and 27% of total cyst registered). Cysts seemed to be transported in an eastward direction after deposition and accumulated in an extensive area that probably is the seedbed responsible for the initiation of HABs in the region. The nGC is a retention area of cysts (and sediments) that permit the formation of seedbeds that could be important for G. catenatum HAB development. Our results provide key information to understand G. catenatum ecology and specifically, to understand the geographic and temporal appearance of HABs in the nGC. [ABSTRACT FROM AUTHOR]

Background. The Gulf of Mexico (GOM) is a semi-enclosed sea where the waters of the United States, Mexico and Cuba converge. Al least 21 species of cetaceans inhabit it. The only mysticete (baleen whale) is found in the northeast (U.S. waters). The distribution of the 20 species of odontocetes (toothed cetaceans) is well understood in U.S. waters, but practically unknown in Mexican and Cuban waters. In this study we used sighting data from several odontocete species to construct habitat suitability maps in order to identify geographical regions suitable for high diversity throughout the GOM. Methods. Historical datasets of georeferenced sightings from across the GOM were used to implement the maximum entropy algorithm (MaxEnt) to model the habitat suitability of each species. Five environmental predictors were used, selected for their influence over the occurrence of cetaceans: two oceanographic predictors (sea surface temperature and chlorophyll-a concentration), and three bathymetric predictors (depth, slope, and distance to 200-m isobath). A spatial approach based on the habitat suitability maps was used to identify the suitable regions. Results. Only 12 species were modeled, which were the ones with the minimum sample size required. The models performed well, showing good discriminatory power and slight overfitting. Overall, depth, minimum sea surface temperature, and bottom slope were the most contributing predictor in the models. High suitability areas of 10 species were located on the continental slope, and four suitable regions were identified: (1) the Mississippi Canyon and the Louisiana-Texas slope in the northern GOM, (2) the west Florida slope in the east-northeastern GOM, (3) the Rio Grande slope in the westnorthwestern GOM, and (4) the Tamaulipas-Veracruz slope in the west-southwestern GOM. Conclusions. We were able to detect four geographic regions in the GOM where a high diversity of odontocetes is expected, all located on the continental slope. Although the methodology to identify them (spatial overlap) is a very conservative approach, it is useful for conservation and management purposes. The paucity of data did not allow all species to be modeled, which highlights the importance of establishing transboundary monitoring programs. [ABSTRACT FROM AUTHOR]

Yellowfin tuna (YFT, Thunnus albacares) is a commercially important species targeted by fisheries in the Gulf of Mexico (GM). Previous studies suggest a high degree of residency in the northern GM, although part of the population performs movements to southern Mexican waters. Whether YFT caught in southern waters also exhibit residency or migrate to the northern gulf is currently uncertain, and little is known regarding their trophic ecology. The isotopic composition (bulk & amino acids) of YFT muscle and liver tissues were compared to a zooplankton-based synoptic isoscape from the entire GM to infer feeding areas and estimate Trophic Position (TP). The spatial distribution of δ15Nbulk and δ15NPhe values of zooplankton indicated two distinct isotopic baselines: one with higher values in the northern GM likely driven by denitrification over the continental shelf, and another in the central-southern gulf, where nitrogen fixation predominates. Based on the contribution of the two regional isotopic baselines to YFT tissues, broad feeding areas were inferred, with a greater contribution of the northern GM (over a one-year time scale by muscle), and to a lesser extent in the central-southern GM (over the ca. 6-month scale by liver). This was corroborated by similarities in δ15NPhe values between YFT and the northern GM. TP estimates were calculated based on stable isotope analysis of bulk (SIA) and compound-specific isotope analysis (CSIA-AA) of the canonical source and trophic amino acids. Mean TP based on SIA was 4.9 ± 1.0 and mean TP based on CSIA-A was 3.9 ± 0.2. YFT caught within the Mexican region seem to feed in northern and in central and southern GM, while feeding in the northern GM has a temporal component. Thus, management strategies need to consider that YFT caught in US and Mexican waters are a shared binational resource that exhibit feeding migrations within the GM. [ABSTRACT FROM AUTHOR]

Samples of the shovelnose guitarfish Pseudobatos productus were collected on board a vessel and at landings of artisanal commercial fisheries in the Gulf of California from May 2004 to June 2007. Samples of 650 females, 2047 embryos and 484 uterine eggs were examined. The reproductive cycle is annual, ovulation and parturition occur in July, the uterine eggs are in diapause for 9 months (July-March) before an accelerated growth of embryos of 3 months. Histological analyses of the uterine wall of pregnant females suggested that no secretions were used for embryo nourishment. The standard percentage of water content was 48·6% in fertilized eggs and 80·75% in full-term embryos. Dry mass loss during embryonic development was 16·3% and the chemical balance of development was 0·84. This indicates that P. productus is a strictly lecithotrophic, viviparous species, that makes no maternal contribution of nutrients during embryonic development. [ABSTRACT FROM AUTHOR]

White Seabass ( Atractoscion nobilis ; Sciaenidae) comprise an important commercial resource in the USA and Mexico, but there are few growth rate estimates and its population structure remains uncertain. Growth rates were estimated based on otolith analysis of fish collected at three locations spanning 1000-km. Variations in growth rates were assessed at the population level and by reconstructing individual growth trajectories. Seabass were sampled from fisheries operating off southern California (SC) and the northern and southern (NBC and SBC) Baja California peninsula from 2009 to 2012 ( n = 415). Ages ranged from 0 to 28-years, but fish >21-years of age were sampled infrequently. Size-at-age was highly variable, particularly for fish <5-years. White Seabass grew quickly during the first 8-years of life after which growth rates decreased considerably. Fitting the size-at-age data with the von Bertalanffy growth function and applying the likelihood ratio test to parameter estimates indicated that SC, NBC and SBC did not differ significantly in growth rates (0.18–0.19-yr −1 ) or asymptotic length (141-cm total length). Individual otolith growth trajectories showed high variability within regions and there were only significant differences in the average width of the first annuli. However, residual analysis of the average annual radii suggests fish from SBC had a larger size-at-age. Those differences may be related to the higher coastal temperatures found in southern coastal waters. Although growth rates may differ during the first year of life, findings suggest growth to be similar across the study range. [ABSTRACT FROM AUTHOR]

Exposure risk is assessed based on modeling suitable habitat of large pelagic fish and oil spill scenarios originating at three wells located in the western GM's deep waters. Since the fate of the oil depends on the oceanographic conditions present during the accident, as well as the magnitude and duration of the spill, which are not known a priori, the scenarios used are a statistical representation of the area in which oil spilled from the well could be found, given all possible outcomes. The ecological vulnerability assessment identified a subset of bony fish with low-medium vulnerability and elasmobranchs with medium-high vulnerability. The oiling probability and exposure risk of both bony fish and elasmobranchs hotspots vary by well analyzed. Thus, these results provide essential information for a risk management plan for the assessed species and others with economic or conservation importance distributed in the GM and worldwide., (Copyright © 2022 Elsevier Ltd. All rights reserved.)