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Predictors of total sardine catch and sardine catch per unit effort in the Sea of Cortés.
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Small pelagic fish constitute 25–40% of the fisheries landings in Mexico. More than 70% of these landings, predominantly Pacific sardine (Sardinops caeruleus), are captured in the Gulf of California. Small pelagic fishes are a key component of the Gulf's ecosystem; they are eaten by seabirds, sea mammals, and other fishes. The sardine fishery withi...
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... the regression model accounted for 81% of the variance in the sardine catch, the true predictive capacity of the model, as estimated by the extrapolated predictions of the jackknifed model, accounted for 54% of the vari- ation in the catch data. In the case of sardine CPUE (Table 1, Fig. 6b), the best predictor was the proportion of sardines in the diet of the Elegant Tern, followed by the breeding success of the Heermann's Gull and by the interaction between the SST anomaly of May-June in the mid-Gulf and the proportion of sardines in the diet of the Elegant Tern. In this case, the regression accounted for 96% of the observed variation, and the predictions of the jackknifed model accounted for 73% of the variation in CPUE. ...
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... We hypothesize that dissimilar marine environmental conditions will result in differences in the diet. We expected that the diet of the San Pedro Mártir colony, being reliant on predictable food resources, would be strongly influenced by temporal changes, especially in response to environmental variations (e.g., El Niño-Southern Oscillation), resulting in significant shifts in productivity and prey availability (Velarde et al., 2004;. In contrast, the Peña Blanca colony in oligotrophic waters will be less affected by the changes in prey abundances, thus expected to show less variability across the breeding season (e.g., Lerma et al., 2020). ...
DNA metabarcoding and stable isotope analysis have significantly advanced our understanding of marine trophic ecology, aiding systematic research on foraging habits and species conservation. In this study, we employed these methods to analyse faecal and blood samples, respectively, to compare the trophic ecology of two Red-billed Tropicbird (Phaethon aethereus; Linnaeus, 1758) colonies on Mexican islands in the Pacific. Trophic patterns among different breeding stages were also examined at both colonies. Dietary analysis reveals a preference for epipelagic fish, cephalopods, and small crustaceans, with variations between colonies and breeding stages. Isotopic values (δ15N and δ13C) align with DNA metabarcoding results, with wider niches during incubation stages. Differences in diet are linked to environmental conditions and trophic plasticity among breeding stages, influenced by changing physiological requirements and prey availability. Variations in dietary profiles reflect contrasting environmental conditions affecting local prey availability.
... The regional climate is influenced by the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), factors contributing to substantial oceanic changes (Luch-Cota et al., 2013). In recent decades, the Gulf of California has experienced pronounced warming, affecting a multitude of marine species and habitats (Nevaŕez-Martıńez et al., 2001;Velarde et al., 2004;Favoretto et al., 2022;Sańchez-Cabeza et al., 2022). It features distinct latitudinal gradients in sea surface temperature and chlorophyll-a concentrations, which delimit three primary oceanographic regions (Brusca, 2010;Ulate et al., 2016). ...
... The eastern lagoons are heavily exploited for agriculture, aquaculture, settlement, and fishing. In contrast, the western bays and inlets face pressures from coastal development and mining activities (Álvarez-Borrego, 1983;Nevaŕez-Martıńez et al., 2001;Velarde et al., 2004;Gonzaĺez-Abraham et al., 2015;Paéz-Osuna et al., 2016;Sańchez-Cabeza et al., 2022). These cumulative pressures threaten the most favorable habitats for seagrass meadows, underscoring the urgency to address current and future anthropogenic threats in the Gulf of California. ...
Seagrasses are globally acknowledged as crucial habitats as they provide a variety of ecosystem services. Mexico’s legislation protects most of these marine plants; however, the protection often fails in application. The Gulf of California, despite being a biodiversity hotspot, has scant data on seagrasses. Here, human activity and climate change increasingly threaten these coastal ecosystems, with conservation and research efforts lacking coordination at a regional level. Our manuscript aimed to review and standardize existing data on Gulf of California seagrass species, ensuring open access for data updates; pinpointing conservation deficiencies; and guiding future research. We have added new records to the official public data, but we were able to recapture only 25% of the seagrass locations meaning a potential reduction in their historical distribution of 45.8%. Even though Mexico’s legislation protects some species of seagrasses, it protection often fails in the application. We identified that only 6.1% of the seagrass locations are within protected areas that recognize their presence in their management plans (e.g., the Balandra Flora and Fauna Protected Area and the Upper Gulf of California and Colorado River Delta Biosphere Reserve). At least 55.9% of seagrass records are associated with potentially damaging activities like pollution, coastal modification or biological resources use, while 23% are exposed to higher frequency of marine heatwaves. Given the importance of seagrass meadows under Mexican law and their internationally recognized ecological value, sharing current information and guiding research is essential. Our study seeks to galvanize renewed research initiatives and raise more awareness on the conservation of the Gulf of California’s seagrasses.
... Additional contextual information has to be obtained to distinguish between climate effects on the relevant ocean biophysics vs fishery effects (and other factors) that affect indicator species' population change (e.g. Velarde et al. 2004, Crawford et al. 2015, Wells et al. 2017, Ainley et al. 2018b. That is, we have to know specifically, and quantitatively, what processes were indicated by the changes in an 'indicator's' population or demography. ...
Among the longest Antarctic biological time series is that of Adélie penguin Pygoscelis adeliae population size at Cape Royds, 1955 to the present. Demographic trends over the 66 years fall into five periods: 1) decrease then recovery due to control of tourism from McMurdo Station/Scott Base; 2) further increase responding to the removal of > 20 000 trophically competing Antarctic minke whales Balaenoptera bonaerensis from the colony's wintering area; 3) stabilization but not decrease upon the ban of whaling in 1982, and whale recovery, owing to increased winds facilitating McMurdo Sound Polynya presence (easier ocean access during nesting); 4) decrease in 2001–2005 when two mega-icebergs, B15A/C16, opposed the wind effect by increasing sea-ice cover, thus limiting ocean access; and 5) after iceberg departure, minimal recovery due to the increased velocity of the wind-generated Ross Gyre reducing penguin breeding probability. A multivariant model using 1998–2018 data confirmed the roles of gyre speed (negative) and open water (positive) in colony growth. Additional negative influence came from high nest predation by south polar skuas Stercorarius maccormicki , reducing chick production, as well as perhaps increased trophic competition from nearby Weddell seals Leptonychotes weddellii . Clearly, long time series increase our understanding of penguin population dynamics responding to a complexity of factors.
... Los intrínsecos se refieren a la capacidad de las aves para obtener alimento, cuidar y alimentar a las crías, entre otros (Vieyra et al., 2009). Los factores extrínsecos hacen referencia a factores ambientales como la presencia de un sitio óptimo para la anidación, abundancia del alimento y los cambios en la dinámica océanoatmósfera, tales como, los cambios en la temperatura superficial del mar (TSM), el viento, los procesos de enriquecimiento por afloramientos de nutrientes del fondo hacia la superficie (surgencias) y las teleconexiones climáticas (Velarde et al., 2004;Barbraud & Weimerskirch, 2005;Vieyra et al., 2009). Estos eventos repercuten en el aumento y disminución de la productividad primaria marina, impactando en las poblacionales de peces, como pelágicos menores (sardinas, anchovetas, etc.), los cuales son alimento básico de organismos en los niveles más altos de la cadena trófica como, por ejemplo, la gran mayoría de las especies de aves y mamíferos marinos, peces pelágicos mayores y del calamar gigante (Bakun & Nelson, 1991;Velarde et al., 2004;Bakun, 2006;Velarde et al., 2014;Bakun et al., 2015;Kampf & Chapman, 2016a). ...
... Los factores extrínsecos hacen referencia a factores ambientales como la presencia de un sitio óptimo para la anidación, abundancia del alimento y los cambios en la dinámica océanoatmósfera, tales como, los cambios en la temperatura superficial del mar (TSM), el viento, los procesos de enriquecimiento por afloramientos de nutrientes del fondo hacia la superficie (surgencias) y las teleconexiones climáticas (Velarde et al., 2004;Barbraud & Weimerskirch, 2005;Vieyra et al., 2009). Estos eventos repercuten en el aumento y disminución de la productividad primaria marina, impactando en las poblacionales de peces, como pelágicos menores (sardinas, anchovetas, etc.), los cuales son alimento básico de organismos en los niveles más altos de la cadena trófica como, por ejemplo, la gran mayoría de las especies de aves y mamíferos marinos, peces pelágicos mayores y del calamar gigante (Bakun & Nelson, 1991;Velarde et al., 2004;Bakun, 2006;Velarde et al., 2014;Bakun et al., 2015;Kampf & Chapman, 2016a). ...
... La disponibilidad del alimento influye en la condición física de las aves marinas, la selección de su área de anidación, la capacidad de producir huevos durante la temporada reproductiva, así como de cuidar y alimentar a sus polluelos. Así, las variaciones en la dinámica océanoatmosfera pueden provocar abundancia o escases de alimento (Velarde et al., 2004;Barrett, 2007;Vieyra et al., 2009;Ancona et al., 2011;Kowalczyk et al., 2015;Velarde et al., 2015;Velarde & Ezcurra, 2018). Ante estos cambios, las aves tienen la capacidad de ajustar su comportamiento, cambiando su dieta y ampliando su zona de forrajeo (Ballance et al., 2006;Ancona et al., 2011;González-Zamora, 2019), cambiando su zona de reproducción, reduciendo el tamaño de sus puestas y el número de crías, aplazando su reproducción y priorizando la supervivencia de los adultos (Barrett, 2007;Vieyra et al., 2009;Lerma-Lizarraga, 2011;Velarde et al., 2015;Velarde & Ezcurra, 2018). ...
... Fresh regurgitations of adult birds of the 2 species were collected during the breeding season in 2017, as the diet for both species included the same species through time (Velarde et al. 1994(Velarde et al. , 2004(Velarde et al. , 2013(Velarde et al. , 2015a; no samples of regurgitation were collected in 2018 and 2019. Regurgitations were collected from adults returning to the colony within a period of approximately 3 h after sunset. ...
The Heermann’s gull and the elegant tern are considered Near Threatened by the IUCN Red List of Threatened Species and under special protection under Mexican environmental law. Close to 95% of the world populations of both species breed on Isla Rasa (Gulf of California). As both species breed on the same island, competition for trophic resources can be expected to be high. Here, the feeding ecology of chicks of both species, as well as the contribution by prey species provided by adults, was studied using stable carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotope analysis in 3 consecutive breeding seasons (2017, 2018, and 2019). Results of the stable isotope analysis revealed that although some segregation in the δ ¹³ C and δ ¹⁵ N values exists between both species, isotopic mixing model outputs indicated that fishes were the most important prey group for both. However, at the prey species level, the most important prey consumed by Heermann’s gulls were northern anchovy, Pacific sardine, and Pacific mackerel, followed by pelagic crab, whereas elegant terns consumed mainly northern anchovy. The trophic width estimated with the stable isotope values during 2017 and 2019 was higher for the Heermann’s gull than for the elegant tern. In contrast, for 2018, the trophic width of the elegant tern was higher than that of the Heermann’s gull. In addition, both species showed a high degree of trophic width overlap during 2017 and 2019 (overlap probability 0.67 and 0.79, respectively). These results highlight the ability of the Heermann’s gull to redirect its food intake to what might be the most accessible prey groups, a feeding strategy that allows the coexistence.
... Seabirds inhabit environments with fluctuating food availability that may vary between and within nesting seasons (Anderson 1989) according to variations in regional-and/or global-scale phenomena, such as sea surface temperature (SST) (Velarde et al. 2004, Velarde & Ezcurra 2018, which is in turn affected by atmospheric conditions (Sánchez-Velaso et al. 2000) and ocean currents (Hoefer 2000), among other drivers. The relationship between environmental parameters and food availability to seabirds is mediated -with some exceptions (Durant et al. 2003, Domínguez-Hernández et al. 2020) -by the effect of SST on phytoplankton and zooplankton production and then the productivity of higher trophic levels such as forage fish, which are food for larger marine species such as seabirds and other ecosystem components (i.e. ...
Seabirds have thrived over time in marine environments with highly variable productivity. Life history strategies favored by natural selection consist of late sexual maturation, few offspring per breeding event, high adult survival, long lifespan, and deferred breeding when food availability is low. Heermann’s gull Larus heermanni , with 95% of its world population breeding on Isla Rasa, Gulf of California, follows this common pattern, including poor breeding performance during periods of low food availability often associated with high sea surface temperatures. Our interest was to characterize individual variations in this general pattern and assess its consequences for lifetime number of fledglings produced. We compared life history parameters from a set of known-age females banded during 1984-1993 and recaptured during 1989-2013 and found that most (85%) followed the general pattern (hereafter ‘conservative’) of laying ≤2 eggs and fledging no chicks during anomalously warm years. However, 15% of the females (hereafter ‘bold’) laid eggs during all anomalously warm years and fledged chicks in most of those years. Throughout their lifespan, conservative females lived significantly longer and produced significantly more eggs, but the total number of fledglings was not significantly different between strategies. Both strategies coexist over time, persisting within the population under conditions that were common until the late 20th century. If conditions continue to vary, with the occurrence of heatwaves and increases in the frequency of anomalously warm years, bold females may have a selective advantage over conservative females, which might help mitigate the impacts of ocean warming on future populations.
... Higher-frequency warming events linked to El Niño, or stochastic weather anomalies, have been responsible for relatively short-lived (1−2 yr) disruptions of the California Current ecosystem (Jacox et al. 2016), and to a lesser degree, the Gulf of Alaska ecosystem (Bailey et al. 1995). These disruptions often in clude negative impacts on seabird breeding success, likely mediated by reductions in the availability of preferred prey (Hatch 1987, Wilson 1991, Velarde et al. 2004, Ainley et al. 2020. One of the largest warm-water events of the 20 th century, the El Niño of 1997−1998 (Chandra et al. 1998), had wide-ranging impacts throughout the Pacific, including a die-off of murres, an increase in murre and kittiwake physiological stress during the following breeding season, chick diet changes, delayed phenology, and reproduction declines and failures , Miller & Sydeman 2004, Gladics et al. 2015. ...
A protracted period (2014-2016) of anomalously warm water in the northeast Pacific Ocean precipitated an extensive die-off of common murres Uria aalge (hereafter ‘murres’) during 2015-2016, accompanied by reduced colony attendance and reproductive success of murres and black-legged kittiwakes Rissa tridactyla (‘kittiwakes’) starting in 2015. Most murres died of starvation following a large-scale reduction in abundance and quality of forage fish. To assess murre and kittiwake recovery following the marine heatwave, we monitored their demographics at 2 colonies (Chisik and Gull Islands) in Cook Inlet, Alaska (USA), from 2016 to 2019. Compared to historic data (1995-1999), we observed declines and increased variability in colony attendance and productivity across species and colonies, and predation was widespread. At Chisik, where food limitations were common during historic studies, both species experienced substantial population declines and reproductive failures in all 4 years (2016-2019) following the heatwave. At Gull, a typically productive colony during historic studies, murres failed to fledge chicks for 3 years (2016-2018) following the heatwave. By 2019, murre productivity recovered to about half that observed during historic studies (0.28 vs. 0.54 chicks per pair), but populations had declined by half. Kittiwake population size at Gull declined a quarter from historic counts, and reproduction alternated between complete breeding failures (2016/2018) and high productivity (2017/2019). These multi-year demographic impacts indicate lingering effects of the heatwave on kittiwakes and murres through forage fish depletion and increased predator disturbance, and possibly other stressors. It remains unknown whether populations can rebound to historic levels. If so, recovery would likely take decades.
... Changes in the diet of plunge diving terns can also be used as indicators of changes in fish stocks. The catch per unit effort of Pacific sardines (Sardinops caeruleus) was predicted with an accuracy of 73% with a model using the proportion of Pacific sardines in the diet of Elegant Terns (Sterna elegans), the reproductive success of Heermann's Gulls (Larus heermanni) and the spring sea surface temperature anomaly in the Sea of Corte's, Baja California (Velarde et al. 2004). There are numerous studies of changes in the diet of plunge diving terns worldwide, apparently related with changes in fish stocks, such as Crested Terns (Sterna bergii) feeding on sardines (Sardinops sagax) in the Gulf of St Vincent, South Australia (McLeay et al. 2009). ...
... (Halfar et al. 2005;Ulate et al. 2016); whereas northward, the colder conditions and higher productivity favor octocorals even in the shallow waters (Ulate et al. 2016). Recent and rapid changes in oceanographic conditions reported in the Gulf of California, especially temperature, are influencing marine communities and fishery catches (Velarde et al. 2004;Lluch-Cota et al. 2010;Robinson et al. 2016;Giron-Nava et al. 2021). Therefore, we wanted to see how gradual warming and extreme heatwaves influenced the temperature dynamics over the central marine sector, and how reef assemblages' composition has been affected. ...
... Warming waters reconfigured communities in rocky reefs from Australia (Wernberg et al. 2013;Marzloff et al. 2016;Tuckett et al. 2017;Smith et al. 2021), the Mediterranean Sea (Bianchi 2007;Bianchi et al. 2018;Bianchi et al. 2019;Azzola et al. 2022), the Atlantic (Kaimuddin et al. 2016;McLean et al. 2021), and in North America (Filbee-Dexter and Wernberg 2018;Beas-Luna et al. 2020;Osland et al. 2021). Events of rapid warming were also observed in correspondence to heatwaves in Australia (Tuckett et al. 2017) and in correspondence to El Niño phases in the Gulf of California (Velarde et al. 2004;Lluch-Cota et al. 2010;Páez-Osuna et al. 2016;Robinson et al. 2016). The 2015 El Niño in particular, was relatively stronger than the recorded one and had effects in different areas of the Gulf of California (Sanchez-Cabeza et al. 2022) with detrimental effects in the Eastern Pacific as well (Kintisch 2015;Zhu et al. 2017;Jackson et al. 2018;Beas-Luna et al. 2020). ...
Globally, marine communities are experiencing gradual warming and extreme heatwaves causing species to shift in geographic range. As a result, the biological assemblages outside tropical latitudes are being reorganized or "tropicalized" as warm-affinity species become increasingly dominant and cool water species recede, with impacts on our economies, food supply, and health. In the Gulf of California, existing oceanographic discontinuities shape marine communities by creating different assemblages according to environmental affinities. In this study, we show how a known ecological boundary underwent a northward shift of 1.5°latitude because of an average 1°C gradual warming over the last decade (2010-2020) and extreme marine heatwaves threefold more frequent. Such shift homogenized environmental conditions and reconfigured rocky reefs communities. Fish biomass decreased of 43%, whereas invertebrates, which recorded a 35% decrease in overall abundance, showed different community configurations depending on the climate regime. Stony coral species with warm water affinities increased with a reduction of cold-water species during the last El Niño. The long-term consequences of the tropi-calization of these rocky reefs' communities are still uncertain. This study underlines the importance of long-term monitoring of key habitats to quantify, predict, and adapt to future climatic stresses.
... Regarding factors unrelated to climate change (Table 3), both work groups pointed out natural and unnatural aspects that have a high impact on the Pacific sardine population, such as overfishing (Arreguin-Sánchez et al., 2017;Johnson et al., 2017), pollution (Lluch-Cota et al., 2007;Páez-Osuna et al., 2017), and natural predators, such as sea lions, birds, and sharks (Velarde et al., 2004;Bakun et al., 2010;Koehn et al., 2017;Adame et al., 2020) (Table 3). Interactions with climatic stressors are expected to have moderate consequences for the species and fishing activity in the CCS (Table 4), while the effects of rising temperature and OMZ expansion were considered serious for the species in the GC ( Table 3). ...
... This reduces the proactivity of the stakeholders, but there are approaches to certificate the fishery.de la Puente and de la Lama, 2019 Considered good in Baja California state, since it has meetings with authorities with a certain periodicity; considered bad in Baja California Sur State since there is no approach between authorities and producers The relationship is not very fluid or direct between producers and academia by an absence of approach channels and a lack of funds for research.Appendix B. Adaptive capacity (AC) score of the Pacific sardine fishery and its associated fishery in the GCThe GC population is distributed through the whole gulf, especially during winter and spring when upwelling from the continental shelf fertilize the GC; despite being a population proper of the GC, it is connected to the populations of the CCS Felix-Uraga et al 2005; Bakun et al 2010 Past evidence of recovery 5 There is evidence of collapses caused by El Niño events and its almost immediate recovery Cisneros-Mata et al., 1995: Lluch.Belda et al., 2003; Bakun et al., 2010 Value/importance 5It is a species of commercial and ecological importance due to the quality of its meat; besides that, it is the most abundant small pelagic fish in the GCVelarde et al 2004;Bakun et al., 2010;Adame et al., 2020 The GC is a relatively low impacted and a very diverse ecosystem where we can find several species of small pelagic fish with a tropical or temperate affinity ...
The Pacific sardine fishery is the most important in terms of catch volume in Mexico. Due to their trophic position, small pelagic fishes respond rapidly and abruptly to ocean climate variability at interannual (ENSO) and decadal time scales (PDO), which is why their response to climate change is expected. The present study applied the Rapid Vulnerability Assessment (RVA) designed for Natural Protected Areas to the context of sardine fishery in northwestern Mexico, expecting that the vulnerability of the fishery to climate change will be the same in the two main fishing areas. The results demonstrate that the RVA is a useful and lissome method, integrating all stakeholders knowledge, including the academic perspective, and serves as an adaptive strategic planning tool upon climate change. Also, because of its dynamics, it was shown to promote co management practices due to the collaborative consensus reached. The sardine fishery from the Gulf of California was considered as the most vulnerable to climate change due to the potential exchange of tropical species of lower commercial value; while environmental changes are expected to favor such fishery in the Pacific along Baja California peninsula. We recommend working on adaptation measures to lower the risk presented by overfishing, and address efforts towards the certification of the fishery in the Pacific region.
