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The Working Group II contribution to the IPCC Sixth Assessment Report assesses the impacts of climate change, looking at ecosystems, biodiversity, and human communities at global and regional levels. It also reviews vulnerabilities and the capacities and limits of the natural world and human societies to adapt to climate change.

The frequency and strength of extreme events are increasing due to climate change. These events have the potential to cause mass mortalities and recruitment failure in very short time scale...

Lay summary Gill membrane lipids of two bivalves presented specific regulations in response to both environmental and dietary resource variabilities. This highlights the importance of considering both trophic and physiological processes when studying responses to environmental stressors; an approach that can be defined as ‘trophic ecophysiology’., Bivalves’ physiological functions (i.e. growth, reproduction) are influenced by environmental variability that can be concomitant with trophic resource variations in terms of quality and quantity. Among the essential molecules that bivalves need to acquire from their diet to maintain physiological functions, fatty acids (FAs) such as polyunsaturated fatty acids (e.g. 20:4n-6 (arachidonic acid), 20:5n-3 (eicosapentaenoic acid) and 22:6n-3 (docosahexaenoic acid)) have been described to play a critical role. The present study examined the FA composition of gill membrane lipids of two bivalve species, Nodipecten subnodosus and Spondylus crassisquama, sampled in a coastal lagoon of the Northeastern Pacific (Ojo de Liebre, Mexico), at two contrasting locations (inner versus outer part of the lagoon) and at two different periods (February and August 2016). Spatiotemporal variations showed that FA composition of gill membrane lipids was highly correlated to FA composition of reserve lipids from digestive gland. This highlights the marked impact of the diet on FA composition of gill membranes. Interestingly, both species presented differences in the seasonal accumulations of plasmalogens and of particular FA that are not found in their diet (e.g. non-methylene interrupted FA, 22:4n-9trans, 20:1n-11), suggesting specific regulations of FA incorporation and lipid class composition in gill membranes to maintain optimal membrane function in their specific and changing environment. This study highlights the importance to characterize the spatial and temporal variability of food resources in order to apprehend the physiological consequences of environmental variability, as well as species differential regulation capacities in a changing world.

Within the marine environment, the rocky shores are recognized for their high species diversity and particularly transitional zones represent areas of biotic mix, promoted by historical and ecological natural variations that allow the presence of taxa from different regions and which present dissimilar biological traits. An extensive survey describes the benthic macroalgae, macroinvertebrates (molluscs, crustaceans, and echinoderms), and fish assemblages at two rocky reefs, Islas Marietas and near Tehuamixtle, in a tropical-temperate transitional zone in the Pacific waters of central Mexico using traditional ecological indices (richness, diversity, and evenness) and complementary taxonomic distinctness indices. Biological material inside each of ten randomly-chosen quadrants (25 × 25 cm) placed along two 50 m transects oriented parallel to the coastline, between 6 and 2 m depth was collected. From field collections, 204 species were identified: macroalgae (22), molluscs (55), crustaceans (78), echinoderms (11), and fish (38). The structure of macroalgae, macroinvertebrates and fishes was similar between sites. Species of macroalgae, molluscs, and fishes were more diverse in summer; crustaceans and echinoderms were more diverse in winter. Our results and the literature suggest a latitudinal pattern of lower seasonal changes in echinoderms and crustaceans at high latitudes, as compared to southern regions of the Mexican tropical Pacific. En el medio marino, las costas rocosas son reconocidas por su alta diversidad de especies y particularmente las zonas de transición representan áreas de mezcla biótica, provocado por las variaciones naturales históricas y ecológicas que permiten la presencia de taxones de diferentes regiones y que presentan rasgos biológicos diferentes. Un estudio intensivo permitió describir los ensambles de macroalgas, macroinvertebrados (moluscos, crustáceos y equinodermos) y de peces en dos arrecifes rocosos: Islas Marietas y Tehuamixtle, en la zona de transición tropical-templado en el norte del Pacífico de México, utilizando índices ecológicos tradicionales (riqueza, diversidad y uniformidad) y complementando con índices de distinción taxonómica. Se colectó el material biológico de 10 cuadrantes (25 × 25 cm) ubicados aleatoriamente a lo largo de dos transectos de 50 m paralelos a la línea de costa, a una profundidad de entre 6 y 12 m. Se identificaron 204 especies: 22 macroalgas, 55 moluscos, 78 crustáceos, 11 equinodermos y 38 peces. La estructura de la comunidad de macroalgas, macroinvertebrados y peces fue similar entre los sitios. Macroalgas, moluscos y peces fueron más diversos en verano y crustáceos y equinodermos fueron más diversos en el invierno. Los resultados y la literatura sugieren un patrón latitudinal de menores cambios estacionales en equinodermos y crustáceos en las altas respecto a bajas latitudes en el Pacífico mexicano.

Documentary scientific evidence supports the notion that the small pelagics fishery in the Gulf of California does not measurably affect the physical habitat or the functional relationships between the species comprising the pelagic ecosystem. Also, there is little information that suggests any negative effects of the small pelagic fishery operations on critically endangered, endemic species, i.e., vaquita and totoaba. Under the current management regime, small pelagics fishery in the Gulf of California has recovered twice from collapses during the last 30 years. Although the small pelagics abundance varies greatly, the long-term productivity of the target species and the structure and function of the pelagic ecosystem are not compromised because the fishery relies on a suitable logistic and administrative platform, which is consistent with international standards for responsible fisheries, precautionary approach and ecosystem-based fisheries management principles.

La literatura gris suele considera se como una fuente de información cuestionable en revistas y publicaciones científicas debido a que carece de una revisión especializada ya que puede constituirse de documentos difíciles de rastrear. Sin embargo, brinda información detallada y de calidad que no se encuentra en las publicaciones con arbitraje estricto. Con el objetivo de ilustrar la importancia de la literatura gris en el ámbito de la ecología pesquera, se realizó una búsqueda en línea de publicaciones en revistas indexadas, en tesis de grado, re portes técnicos y resúmenes de congresos donde se reportan las relaciones tróficas de los pelágicos menores con especies de diversos taxa en el Golfo de California. Se obtuvo un total de 57 referencias bibliográficas de las cuales 36 son consideradas como literatura gris. Excluir los datos contenidos en estas fuentes de los análisis que se lleven a cabo sobre el tema, podría representar una pérdida de más del 60% de la información disponible. Este sesgo tiene el potencial de producir conclusiones incompletas o erróneas en los estudios de la dinámica trófica de los pelágicos menores en el Golfo de California.

Annually averaged sea surface temperature anomalies at four 2°x2° quadrants at the Gulf of California, Mexico) were constructed using ICOADS (International Comprehensive Ocean-Atmosphere Data Set) and ERSST (NOAA Extended Reconstructed SST data set), contrasted to similar latitudinal quadrants at the Pacific coast of the Baja California peninsula to assess their independent variation, given the way ERSST data are constructed by geographical interpolation and their close vicinity to the Pacific coast. Later they were compared to large scale environmental indices (Pacific Decadal Oscillation index, PDO; and Nino 3 index, N3) to examine their relationships. Hamming filters were utilized to isolate high (20 years) frequencies for comparison. The relationships of the decadal scale variation and the relative abundance of stocks being harvested by two outstanding fisheries (penaeid shrimps and California sardine) are explored given their strong response to environmental variations because of their short life cycle and fast growth.

The Gulf of California is unique because of its geographical location and conformation. It hosts diverse ecosystems and important fisheries that support industry and provide livelihood to coastal settlements. It is also the site of interests and problems, and an intense interaction among managers, producers, and conservationists. In this report, we scrutinize the abiotic (hydrography, climate, ocean circulation, and chemistry) and biotic (phyto- and zooplankton, fish, invertebrates, marine mammals, birds, and turtles) components of the marine ecosystem, and some particular aspects of climate variability, endemisms, harmful algal blooms, oxygen minimum layer, and pollution. We also review the current conditions and conflicts around the main fisheries (shrimp, small and large pelagic fishes, squid, artisanal and sportfishing), the most important human activity in the Gulf of California. We cover some aspects of management and conservation of fisheries, especially the claimed overexploitation of fish resources and the ecosystems, and review proposals for creating networks of marine protected areas. We conclude by identifying main needs for information and research, particularly the integration of data bases, the implementation of models and paleoreconstructions, establishment of monitoring programs, and the evaluation of fishing impacts and management actions.

Using the Ecopath with Ecosim software, a trophic structure model of the Northern Gulf of California was constructed to represent the main biomass flows in the system. It was based mostly on bibliographic data and provides a snapshot of how the ecosystem operates. The model consisted of 29 functional groups. The total system throughput was 6633 tonnes/km2 per year, from which 51.7% are for internal consumption, 20.0% are for respiration, 16.0% becomes detritus, and 12.2% are removed through commercial fishing. Main results show that most groups were impacted more by predation and competition than by fishing pressure, and that there are some characteristics that indicate that use of the ecosystem is balanced.

The Gulf of California on Mexico’s west coast is approximately 1,250 kilometers long, with a climate ranging from temperate to tropical and flanked on both sides by deserts. It has great biological diversity, extreme tides and water characteristics, and is geologically active. The Atlas has a page for each scientific cruise, that could be found, in the Gulf since 1825 to nearly the present. Each page describes the cruise and displays a schematic cruise pattern. The Introduction is in English and Spanish. After the Introduction is a list of key words that have been used to describe the data collected and instruments used, but any word or words can be used to search the Atlas.

The information on the transitional areas between the temperate and tropical domains at the southern extent of the California Current System is reviewed and described, particularly searching for the relative isolation or interchange between the western coast of the Baja California peninsula and the Gulf of California, as well as mechanisms that permit the existence of sizeable stocks of California sardine. Biological Action Centers that have high productivity throughout the year, as opposed to the rest of the coastal area, are found in both the western coast of the peninsula at the Sebastián Vizcaíno—Punta Eugenia region and in the Ballenas Channel inside the gulf; these features support large biomasses of sardine throughout the full year and serve as long term refuges during adverse periods. The role of the Sebastián Vizcaino sardine stock as the primary group for expansion is examined.

"El manejo de las poblaciones de pelágicos menores demanda enormes esfuerzos de investigación, debido a su fuerte dependencia del ambiente. A pesar de haberse iniciado y desarrollado en regiones distantes, a diferentes tiempos y bajo esquemas de manejo diversos, las pesquerías de pelágicos menores del mundo comparten una historia de fluctuaciones de baja frecuencia (entre décadas), aproximadamente sincrónicas e independientes de los niveles de explotación. A otras escalas temporales (entre años), el ENSO representa la fuente de variabilidad más importante afectando características fisiológicas y ecológicas. Con la finalidad de considerar estas fuentes de variaciones en la biomasa de poblaciones en explotación, las ciencias pesqueras modernas se ven en la necesidad de incorporar enfoques de investigación multidisciplinarios e innovadores. Una posible ruta es estudiar procesos biológicos clave, las fuentes y mecanismos de estrés ambiental, modelar estas relaciones e implementar sistemas de información como herramientas para un manejo adecuado. Actualmente se sabe que el reclutamiento en pelágicos menores es altamente variable, y existen una serie de hipótesis respecto de los mecanismos mediante los cuales varía el éxito de reclutamiento. Al tratar de abordar estudios a escala regional, una posibilidad es adaptar dichas hipótesis a las condiciones locales mediante la selección de información pertinente, y la incorporación apropiada de técnicas de análisis y modelos. En este contexto, se puede considerar a la sardina de Golfo de California como un laboratorio natural para este tipo de enfoques de investigación, gracias a sus características ambientales y el grado de conocimiento del recurso. De manera similar a lo que ocurre en otras regiones pesqueras de pelágicos menores, este recurso es de importancia regional dado que representa una alta proporción de la captura nacional total; sin embargo, también representa uno de los recursos más variables. En la baja frecuencia, la sardina del golfo y la del sistema de la Corriente de California deben ser consideradas juntas y en sincronía con la señal del Régimen. En la alta frecuencia, el ENSO produce efectos directos en los movimientos anuales de distribución, los niveles de captura, el éxito reproductivo y el tamaño de las clases anuales..." "Management of small pelagic fisheries is very research dernanding due to their high environment-depending variability. Besides these fisheries have developed in different regions, times, and management approaches, they share a riearly synchronic decadal-scale growinglcollapsing history, independently from exploitatiori levels. At the interannual scale, the ENSO is the most important source of variability driving direct physiological effects and ecological alterations. To contemplate these source of biomass variation, Nlodern fishery sciences must achieve new multidisciplinary and innovative research approaches. One possible route is to study key biological processes, the environmental sources and mechanisms underlying the variations in those processes, modeling the relations arid implementing information systems as tools for suitable management. Regarding small pelagic fish, it has being already demonstrated recruitment is highly variable, and there is a nuinber of integrative hypotheses already developed. At regional scale, one could try to adapt those tiypotheses to local conditions, by the proper selection of data sources, analyzing technics, arid models. The Gulf of California sardine is a suitable case for designing environmental iriformation systems due to a number of properties. As in other regions, this fishery is massive and regionally irnportant, but also highly variable. In the low frequency, the Gulf of California and the Califorriia sardine stocks should be regarded as one, and the system seems to be in synchrony with the Regime signal. At the high frequency, ENSO has apparent effects on southward movement , catch levels, reproduction, and strength of year classes. Winter wind-driven upwelling at the continental side is the key process controlling enrichment in the central Gulf, where most of the sardine spawriiiig takes place. One product of this work is the computation of an upwelling index, the analysis of the resulting series and its incorporation to the analysis. Temperature and the triad processes are key stress sources controlling recruitment fluctuations in the Gulf of California sardine. A double-logistic function was designed and fitted to represent relations between physical variables (SST and UI) and biological processes (spawning success as eggs and larvae positiveltotal sampled stations) with the ability of being dome-shaped, nonlinear, not restricted to symmetry and with predictive value..."

Decade-scale regimes of sardine Sardinops sagax and anchovy Engraulis spp. have been observed in the productive coastal waters of the North-Western, North-Eastern and South-Eastern Pacific and the South-Eastern Atlantic. In each of these systems, the two genera fluctuate out of phase with each other. The subdominant genus may initiate a recovery while the other species is still abundant, so population growth is not necessarily a response to a vacant niche. Rather, it appears to be triggered by formation of one or a few powerful year-classes. At high population levels, quality of sardine and their eggs decreased in Japan, leading to decreased production and survival of eggs, poor year-classes and stock collapse. Excessive fishing of strong year-classes early in the recovery stage may prevent a species from assuming dominance, so influencing the natural succession of species. This may greatly alter the structure and functioning of an ecosystem. For example, a mesopelagic forage fish may replace an epipelagic one, with severe repercussions for predators that can only feed in the upper ocean, e.g. some seabirds. Biological factors also may influence the succession of forage fish. For example, off California, peaks in abundance of predatory species such as bonita Sarda, and chub mackerel Scomber, separate those of the planktivorous sardine and anchovy. In the Pacific Ocean, sardine distribution has change greatly. Compared with its range when scarce, a population at a high level of biomass can extend 1 000-1 800 miles farther along the coast and 400-2 200 miles farther out to sea. In different periods of high biomass, sardine did not always have the same distribution. In the 1930s and 1940s, near simultaneous fluctuations of sardine in the North-Western and North-Eastern Pacific were in phase. In the 1980s and 1990s, sardine in the North-Western and South-Eastern Pacific were fluctuating in phase. However, along the west coast of North America, sardine started their most recent increase later than in other regions of the Pacific Ocean. This increase is continuing, whereas sardine populations in the North-Western and South-Eastern Pacific have decreased both in catch and geographic distribution since the late 1980s. Therefore, the North-Eastern Pacific has moved out of phase with other major Pacific sardine populations. This may be because abundance of sardine in the California Current has not yet reached a level at which density-dependent effects exert a major influence. Sardine and anchovy in the South-Eastern Atlantic have been out of phase with populations in the Pacific Ocean, especially those off Peru and Chile. Over the last 300 years, episodic fisheries for Bohuslän herring Clupea harengus in Sweden coincide with periods of high anchovy abundance off California. Near simultaneous fluctuations of fish stocks in widely separated regions support the view that they are sometimes influenced by climate operating at a global scale. Changes of the gyre-scale circulation seem to be major factors in the decadal climate. In Australia, sardine have a wide range, but the less productive waters support a much lower biomass than is found in the other four systems. Engraulis occur in some systems from which Sardinops are absent, for example, Brazil, where they and Sardinella are segregated vertically in the water column.

En este trabajo se relacionan gráficamente la distribución de las concentraciones de pigmentos fotosintéticos derivadas de composiciones mensuales de imágenes producidas por la lectura del sensor Coastal Zone Color Scaner del satélite Nimbus-7, con mapas de abundancia de atún aleta amarilla derivados de los datos de bitácoras de la flota atunera mexicana para el periodo 1984-1986. Los resultados del estudio muestran una relación entre la distribución de frentes de color, independientemente de la concentración de pigmentos. Por otro lado, mediante el uso de series construidas con los promedios mensuales en el área, se reconoce un desfazamiento de aproximadamente una estación (tres a cinco meses) entre los valores máximos de abundancia de atún y concentración de pigmentos.

En el presente estudio se caracterizó la variabilidad ambiental de gran escala (interanual y multidecadal) y sus efectos ecológicos sobre las poblaciones naturales en aguas del Pacífico mexicano y regiones oceánicas adyacentes. A partir de los resultados se identifican tres escalas de variación en el Pacífico mexicano: la escala interanual relacionada con la variabilidad del El Niño/a Oscilación del Sur (ENSO) y la escala cuasidecadal y la multidecadal, asociadas a modos de variación climática del Pacífico Norte. A escala interanual se ha observado que los cambios en la ocurrencia de la ballena de Bryde (Balaenoptera edeni) en la Bahía de La Paz están influenciados por la variabilidad del ENSO y probablemente estén mediados por la disponibilidad de sus presas. A escalas cuasidecadales se observa que los vientos tehuanos son una fuente de variabilidad climática extratropical en el Pacífico Oriental Tropical; esta señal de baja frecuencia en los tehuanos puede ser modelada por la variación extratropical del sistema de alta presión del Pacífico Noreste, siendo su teleconexión el movimiento hacia el sur de los frentes fríos que bajan por Norteamérica desde el Pacífico Noreste. A escala multidecadal se distinguen con claridad la alternancia de periodos de enfriamiento y calentamiento en la Corriente de California durante los últimos 110 años. Estos cambios en la temperatura superficial del mar son indicativos de cambios en la circulación oceánica y atmosférica, que en última instancia, afectan los mecanismos de enriquecimiento de las aguas superficiales en toda la cuenca del Pacífico Norte. Esta señal de baja frecuencia representa la variación del régimen. Las respuestas biológicas documentadas relacionadas con esta escala de variación incluyen: 1) la expansión y contracción de poblaciones de la sardina de California (Sardinops sagax caerulea) y el calamar gigante (Dosidicus gigas), 2) cambios en la distribución en delfines comunes (Delphinus sp.), y 3) cambios en los patrones de migración de la ballena azul (Balaenoptera musculus); asimismo la evidencia sugiere cambios de largo plazo en la distribución de ballena gris (Eschrichtius robustus), ballena de aleta (Balaenoptera physalus), delfín de costados blancos (Lagenorhynchus obliquidens) y cachalotes (Physeter macrocephalus) que podrían estar relacionados con este tipo de variación multidecadal.