Endangered Species and Precarious Lives in the Upper Gulf of California

Sedimentation in the Colorado River delta and Upper Gulf of California after nearly a century of discharge loss

Two semi-analytical algorithms, Generalized Inherent Optical Property (GIOP) and Garver-Siegel-Maritorena (GSM), were evaluated in terms of how well they reproduced the absorption coefficient of phytoplankton (aph(λ)) and dissolved and detrital organic matter (adg(λ)) at three wavelengths (λ of 412, 443, and 488 nm) in a zone with optically complex waters, the Upper Gulf of California (UGC) and the Northern Gulf of California (NGC). In the UGC, detritus determines most of the total light absorption, whereas, in the NGC, chromophoric dissolved organic material (CDOM) and phytoplankton dominate. Upon comparing the results of each model with a database assembled from four cruises done from spring to summer (March through September) between 2011 and 2013, it was found that GIOP is a better estimator for aph(λ) than GSM, independently of the region. However, both algorithms underestimate in situ values in the NGC, whereas they overestimate them in the UGC. Errors are associated with the following: (a) the constant a*ph(λ) value used by GSM and GIOP (0.055 m2 mgChla−1) is higher than the most frequent value observed in this study’s data (0.03 m2 mgChla−1), and (b) satellite-derived chlorophyll a concentration (Chla) is biased high compared with in situ Chla. GIOP gave also better results for the adg(λ) estimation than GSM, especially in the NGC. The spectral slope Sdg was identified as an important parameter for estimating adg(λ), and this study’s results indicated that the use of a fixed input value in models was not adequate. The evaluation confirms the lack of generality of algorithms like GIOP and GSM, whose reflectance model is too simplified to capture expected variability. Finally, a greater monitoring effort is suggested in the study area regarding the collection of in situ reflectance data, which would allow explaining the effects that detritus and CDOM may have on the semi-analytical reflectance inversions, as well as isolating the possible influence of the atmosphere on the satellite-derived water reflectance and Chla.

Montes, J.M.; Lavin, M.F., and Pares-Sierra, A.F., 2016. Seasonal heat and salt balance in the Upper Gulf of California. The salinity and heat balance, as well as the seasonal variation of the average absolute salinity (〈SA〉) and conservative temperature (〈Θ〉), were described by using data from 24 cruises within four domains in the Upper Gulf of California (UGC). Monthly values of SA and Θ, and surface fluxes obtained from ERA-Interim reanalysis data sets were fitted to a seasonal signal, and the horizontal fluxes of salinity and heat content were calculated by using balance equations. The UGC exports salt and heat to the Northern Gulf of California (NGC) almost all year, with an annual mean of 1.6 g/kg per year for the salinity flux and 0.16 terawatts (TW) for the heat flux. The results suggest that the net excess of evaporation (∼0.8 m/y) and heat gain by the surface (∼70 W/m2) are the main factors controlling the exchange of salinity and heat between the UGC and the NGC. To help identify the r...

He completed his undergraduate studies at the Autonomous University of Baja California (UABC) and graduated with the subject: Sedimentology in the Upper Gulf of California. He continued his master's studies at UABC working with Sedimentology and Marine Chemistry in the Upper and Northern Gulf of California.

We tested the hypothesis that dispersal is sex biased in an unexploited population of brook trout, Salvelinus fontinalis, on Cape Race, Newfoundland, Canada. Based on the assumptions that trout are promiscuous and that reproductive success is limited primarily by either number of mates (males) or fecundity (females), we predicted that males would disperse greater distances than females. We also tested the hypothesis that trout populations comprise stationary and mobile individuals, predicting that males have greater mobility than females. Based on a mark-recapture study of 943 individually tagged fishes, 191 of which were recaptured over 5 years, we find strong support for our hypothesis of male-biased dispersal in brook trout. Averaged among all 11 resampling periods, males dispersed 2.5 times as far as females; during the spawning period only, male dispersal exceeded that by females almost fourfold. Both sexes were heterogeneous with respect to movement, with a lower incidence of mobility among females (29.6%) than males (41.1%); mobile males dispersed six times further than mobile females. We conclude that this sex bias reduces mate competition among male kin and decreases the probability that males will reproduce with related females.

Variability of the optical properties of the northern Gulf of California (Mexico) were analyzed for the first time based on six cruises performed from spring to summer (March to September) between 2008 and 2013. The changes observed in the absorption by three seawater components (phytoplankton, detritus and chromophoric dissolved organic matter or CDOM) were analyzed in relation to changes in bio-optical regions and composition of the phytoplankton community (determined based on phytoplankton pigments). Two regions with unique bio-optical characteristics were identified separated by a narrow transition zone: the Upper Gulf of California (UGC) and Northern Gulf of California (NGC). Despite the temporal changes in their spatial distribution they maintained particular characteristic. UGC is characterized by an average Chla of 1.78 mg/m3, the dominance of microphytoplankton (diatoms and dinoflagellates) and a stronger contribution of detritus to total light absorption. NGC is characterized by an average Chla of 0.7 mg/m3 and the predominance of picophytoplankton, characterized by the dominance of zeaxanthin (marker pigment for cyanobacteria) and/or chlorophyll b (marker pigment for green algae), along with a co-dominium by CDOM and phytoplankton to light absorption. Results indicate that Case II waters can be very different when evaluating the individual contribution by phytoplankton, detritus and CDOM to total light absorption what has to be considered for the selection of bio-optical models for each specific region what can also help to a better definition of the related uncertainties.

Sedimentation in the northern Gulf of California after cessation of the Colorado River discharge

The vaquita (Phocoena sinus) is an endemic species of the Upper Gulf of California (UGC), which is in a critical state of extinction. Bycatch has been considered the main factor leading to its potential extinction; however, the impact of the damming of the Colorado River on the species’ ecology has not been studied. Stable isotopes of carbon (δ13C) and oxygen (δ18O) from vaquita bones were analyzed as indicators of the carbon source of primary producers and habitat use in the UGC from 1982 to 1993. Based on the Colorado River’s flow into the UGC, two periods were markedly different: from 1982 to 1988, when freshwater arrived, and from 1989 to 1993, when the flow was null. Sea surface salinity (SSS) data showed the inverse of the river’s flow pattern, being significantly lower at the end of the 1980s than at the beginning of the 1990s. In agreement with the above, sea surface temperature (SST)/SSS diagrams showed the presence of two water masses inside a gradient from 33.8 to 35.2 psu. The δ13C was significantly different between both periods, with a mean value of -9.1‰ at the end of the 1980s and a mean value of -10.8‰ at the beginning of the 1990s. This means that, when the river flow was dammed, the carbon source of primary producers changed significantly in the UGC. However, the δ18O was not significantly different between both periods, with values of 30.4‰ and 30.5‰, respectively. Comparing the vaquita’s average values of δ18O from this study with those of other marine mammals obtained from previous studies revealed that the vaquita is the most enriched marine mammal species, which could be the result of the high evaporation and salinity that currently occur in the UGC, the vaquita’s habitat. A longer temporal series might show changes in δ18O, which have been detected in other species living in the UGC. From a conservation point of view, the results showed that the impact of environmental variability on the trophic ecology of the vaquita has potential effects on the species’ health.

Larval fish assemblages, environment and circulation in a semienclosed sea (Gulf of California, Mexico)

Sediment discharges from rivers play a key role in downstream ecosystems, both for ecosystem morphology (e.g., deltas) and productivity. However, the construction of dams and river regulation dramatically alter sediment transport. Currently, the Colorado River delta is one of the most transformed deltas in the world and, most years, no flow reaches the Gulf of California. In this study, we used satellite images for the observation and measurement of coastal water turbidity in the Upper Gulf of California (UGC) and Colorado River Delta (CRD). Specifically, we used the Earth-observing Satellites (in French Satellites Pour l’Observation de la Terre, SPOT) high spatial resolution satellite. We processed images of the wavelength 2 (S2610-680) from the period between 2008 and 2013 in the Biosphere Reserve area. Results showed that suspended material and high turbidity predominate in the CRD and intertidal zones of the UGC. High and very high turbidity values were due to two opposite coastal transport components along the Sonora and Baja California coasts. The high spatial resolution of the SPOT sensor effectively allowed the sediment transport gradients and the accumulation zones to be located in a highly variable area. This information provided by SPOT images can be very valuable for management decisions such as the amount of ecological flow that needs to be released. This area is the habitat of endangered species, such as totoaba (Totoaba macdonaldi) and vaquita (Phocoena sinus), that are seriously affected by the loss of estuarine conditions. High resolution satellite images can help to quantify the true extent of corrective measures.

Hydrography and circulation in the Northern Gulf of California during winter of 1994–1995

The Gulf of California is an excellent example of how new ocean basins form. Tectonically, the northern Gulf of California is an incipient ocean basin and studies on it have defined acoustic basement and reveal the presence of new oceanic crust and intrusive bodies. Some recent studies report fundamental differences between the basins of the northern and southern Gulf of California: that the latter have well-developed oceanic crust beneath a thin cover of sediments, whereas the northern basins show proto-ocean basins, which may reflect thermal insulation of the thick sedimentary cover, the presence of low-angle faults, and more diffuse and distributed deformation. During the 1970s, Petróleos Mexicanos (PEMEX) undertook a 2D seismic reflection survey in the northern Gulf of California, over many active rift basins, including the Consag Basin. Through the processing and interpretation of these data, we describe the structural characteristics of the Consag Basin beyond 2 km depths. Using seismic reflection data, we identified an intrusion in the central part of this basin that may represent new oceanic crust buried by more than 4 km of sediments.

The Upper Gulf of California is a diverse and highly productive ecosystem supporting some of the most important fisheries in Mexico, yet a history of weak fisheries management and illegal fishing threaten the area’s biodiversity and undermine human well-being in the communities along its shores. The vaquita (Phocoena sinus)is endemic to these waters and is on the brink of extinction due to incidental entanglement in gillnets used by small-scale fishers. The resurgence of an illegal gillnet fishery for totoaba (Totoaba macdonaldi), whose swim bladders are highly prized in Hong Kong and continental China, has accelerated the steep decline of the vaquita population. Vaquita is one of a growing number of cases linking illegal wildlife trade, organized crime, and biodiversity decline. This paper provides a summary of key reflections of a panel of fisheries economists gathered at the ninth forum of the North American Association of Fisheries Economists (NAAFE) to evaluate the policies implemented in the Upper Gulf through an economic lens and updated to reflect more recent developments. The panel recognized that poor fisheries management, lack of effective enforcement, distant demand for an illegal product, corruption, and few viable economic alternatives confound efforts to address vaquita bycatch. The complexity of these problems requires a holistic, multidisciplinary approach, combining top-down, direct regulation and bottom-up, participatory and incentive-based instruments. Addressing chronic deficiencies in enforcement, particularly in the very small area where the remaining vaquitas are found, is crucial to prevent imminent extinction. Equally crucial are sustained actions to support legal fishers able to make a good living – with a direct stake in healthy marine ecosystems – as key components of policies to address bycatch and reduce wildlife trafficking. The situation in the Upper Gulf of California is dire, yet similar threats to other marine mammals and wildlife trafficked species may benefit from the experience of the vaquita.

Since the times of early explorers the Gulf of California has been described as an area of high fertility (Leon-Portilla 1972), owing mainly to tidal mixing and upwelling processes (Alvarez-Borrego et al. 1978).The shallow northernmost part of the Gulf, the Upper Gulf of California, and the Colorado River delta are an area of reproduction and nursery for many fish species (Guevara-Escamilla et al. 1973).They are also habitat for endangered endemic species, like the totoaba (Totoaba macdonaldi) and the small dolphin “vaquita” (Phocoena sinus). In 1993, the Mexican Federal Government decreed the area as a Reserve of the Biosphere (Reserva de la Biosfera del Alto Golfo de California y Delta del Rio Colorado; Fig. 22.1).

Baseline knowledge of spatial and temporal distribution patterns is essential for cetacean management and conservation. Such knowledge is particularly important in areas where gillnet fishing occurs, as the Upper Gulf of California, which increases the probability of bycatch of cetaceans. In this area, the vaquita porpoise (Phocoena sinus) has been widely studied, but the knowledge of other cetaceans is scarce and based on traditional visual survey methods. We used data collected by an array of acoustic click detectors (C-PODs) during the summers 2011 to 2015 to analyze the distribution of dolphins in the Vaquita Refuge in the Upper Gulf of California. We recorded 120,038 echolocation click trains of dolphins during 12,371 days of recording effort at 46 sampling sites. Based on simultaneous visual and acoustic data, we estimated a false positive acoustic detection rate of 19.4%. Dolphin acoustic activity varied among sites, with higher activity in the east of the Vaquita Refuge. Acoustic activity was higher at night than during the day. We used negative binomial generalized linear models to study the count of clicks of dolphins in relation to spatial, temporal, physical, biological and anthropogenic explanatory variables. The best model selected for the response variable included sampling site, day-night condition, and vertical component of tide speed. Patterns in the spatial distribution of predicted acoustic activity of dolphins were similar to the acoustic activity observed per sampling season. Higher acoustic activity was predicted at night, but the tide speed variable was not relevant under this condition. Acoustic activity patterns could be related to the availability of prey resources since echolocation click trains are associated with foraging activities of dolphins. This is the first study of the distribution of dolphins in Mexico using medium-term systematic passive acoustic monitoring, and the results can contribute to better management to the natural protected area located in the Upper Gulf of California.