Hypoxia and Sturgeons: report to the Chesapeake Bay Program Dissolved Oxygen Criteria Team

In this essay, three lines of evidence are developed that sturgeons in the Chesapeake Bay and elsewhere are unusually sensitive to hypoxic conditions: 1. In comparison to other fishes, sturgeons have a limited behavioral and physiological capacity to respond to hypoxia. Basal metabolism, growth, and consumption are quite sensitive to changes in oxygen level, which may indicate a relatively poor ability by sturgeons to oxyregulate. 2. During summertime, temperatures >20 C amplify the effect of hypoxia on sturgeons and other fishes due to a temperature*oxygen "squeeze" (Coutant 1987)- In bottom waters, this interaction results in substantial reduction of habitat; in dry years, nursery habitats in the Chesapeake Bay may be particularly reduced or even eliminated. 3. While evidence for population level effects by hypoxia are circumstantial, there are corresponding trends between the absence of Atlantic sturgeon reproduction in estuaries like the Chesapeake Bay where summertime hypoxia predominates on a system-wide scale. Also, the recent and dramatic recovery of shortnose sturgeon in the Hudson River (4-fold increase in abundance from 1980 to 1995) may have been stimulated by improvement of a large portion of the nursery habitat that was restored from hypoxia to normoxia during the period 1973-1978. (PDF contains 26 pages

Spatio-temporal variability of mid-size pelagic fishes in the Gulf of Cadiz shelf waters in relation to climatic and environmental drivers

Modeling spatio-temporal patterns of mid-size pelagic fish species (MSPFS) distribution and density is of great interest from the standpoint of both their management and conservation. Herein, temporal changes in the spatial patterns of five MSPFS off the Gulf of Cadiz are analyzed from acoustic surveys data (2007-2017). In particular, we evaluated intra-specific variability over time and space and relate such fluctuations to environmental and climatic drivers aimed to provide support to the implementation of a future ecosystem approach to fisheries management in this region

Are Alexandrium catenella Blooms Spreading Offshore in Southern Chile? An In-Depth Analysis of the First PSP Outbreak in the Oceanic Coast

The blooms of Alexandrium catenella, the main producer of paralytic shellfish toxins worldwide, have become the main threat to coastal activities in Southern Chile, such as artisanal fisheries, aquaculture and public health. Here, we explore retrospective data from an intense Paralytic Shellfish Poisoning outbreak in Southern Chile in Summer–Autumn 2016, identifying environmental drivers, spatiotemporal dynamics, and detoxification rates of the main filter-feeder shellfish resources during an intense A. catenella bloom, which led to the greatest socio-economic impacts in that area. Exponential detoxification models evidenced large differences in detoxification dynamics between the three filter-feeder species surf clam (Ensis macha), giant barnacle (Austromegabalanus psittacus), and red sea squirt (Pyura chilensis). Surf clam showed an initial toxicity (9054 µg STX-eq·100 g−1) around 10-fold higher than the other two species. It exhibited a relatively fast detoxification rate and approached the human safety limit of 80 µg STX-eq·100 g−1 towards the end of the 150 days. Ecological implications and future trends are also discussed. Based on the cell density evolution, data previously gathered on the area, and the biology of this species, we propose that the bloom originated in the coastal area, spreading offshore thanks to the resting cysts formed and transported in the water column

Modelling the Spatial and Temporal Dynamics of Paralytic Shellfish Toxins (PST) at Different Scales: Implications for Research and Management

Harmful algal blooms, in particular recurrent blooms of the dinoflagellate Alexandrium catenella, associated with paralytic shellfish poisoning (PSP), frequently limit commercial shellfish harvests, resulting in serious socio-economic consequences. Although the PSP-inducing species that threaten the most vulnerable commercial species of shellfish are very patchy and spatially heterogeneous in their distribution, the spatial and temporal scales of their effects have largely been ignored in monitoring programs and by researchers. In this study, we examined the spatial and temporal dynamics of PSP toxicity in the clam (Ameghinomya antiqua) in two fishing grounds in southern Chile (Ovalada Island and Low Bay). During the summer of 2009, both were affected by an intense toxic bloom of A. catenella (up to 1.1 × 106 cells L-1). Generalized linear models were used to assess the potential influence of different environmental variables on the field detoxification rates of PSP toxins over a period of 12 months. This was achieved using a four parameter exponential decay model to fit and compare field detoxification rates per sampling site. The results show differences in the spatial variability and temporal dynamics of PSP toxicity, given that greater toxicities (+10-fold) and faster detoxification (20% faster) are observed at the Ovalada Island site, the less oceanic zone, and where higher amounts of clam are annually produced. Our observations support the relevance of considering different spatial and temporal scales to obtain more accurate assessments of PSP accumulation and detoxification dynamics and to improve the efficacy of fisheries management after toxic events.This research was funded by FONDEF Project MR07I1007 from the 2nd Program on Red Tides and the project REDI170575 from the International Cooperation Programme of the Chilean National Commission for Scientific and Technological Research (CONICYT). Patricio A. Díaz is funded by the Centro de Biotecnología y Bioingeniería (CeBiB) (PIA project FB0001, ANID, Chile). Rosa I. Figueroa is funded by a national project from the Spanish Ministry of Science and Innovation and the European Community (FEDER) (Project DIANAS-CTM2017- 86066-R), a grant for Galician Networks of Excellence (GRC-VGO- HAB IN607A-2019/04) from the Innovation Agency of the Xunta de Galicia (GAIN) and the structural IEO-CSIC project CCVIEO-7.Peer reviewe

three_years_data_elemental_ratio.csv

Elemental otolith fingerprints from Sparus aurata, collected in four Mediterranean Lagoons by Tournois et al (2013). Used by Niklitschek & Darnaude as a case study<br

Spring northward juvenile migration of the Patagonian grenadier (Macruronus magellanicus) from the Northwest Patagonian waters of Chile

Important nursery grounds for Patagonian grenadier (Macruronus magellanicus) are located mainly in the Northwest Patagonian Inner Sea (42ºS-44ºS), from which juvenile must to disperse or migrate offshore, then along the Chilean coast either northward or southward. The objective of this paper was to estimate northward spring juvenile migration of the Patagonian grenadier from nursery to feeding areas, which are located near Talcahuano (35º00’S-37º10’S). Length-frequency data (LFD) were obtained from an acoustic survey carried out in November 1999, which covered from 35ºS to 47ºS. Generalized linear model was used to describe the presence of juvenile per latitude and depth, and to infer the origin and displacement of juveniles. Subsequently, LFD data were grouped according to latitudinal strata. Grouped LFD were decomposed into normal component groups, from which mean, standard deviation and proportion were estimated from the mixed LFD. The average length of the identified groups were sorted from south to north, and linked to compute significant increment in fish length and age per kilometers. The length increment per time was not due to growth, rather they was due to spatial displacement of juvenile from southern nursery grounds to northern feeding areas. Although homing to feeding areas and/or high residency (partial migration) have been postulated, it seems that recruitment of juveniles to northern feeding areas are origintaed from NPIS nurseries. The West Wind Drift Current seems to be the main drive for dispersion of Patagonian grenadier to recruit northward in open waters along the continental shelf

Tendencias de acumulación y detoxificación natural de veneno paralizante de los mariscos en dos bivalvos del mar interior de la Patagonia Noroccidental

The accumulation of marine toxins in aquatic filterers is a recurrent event that imposes serious risks to human health and important economic losses. While direct monitoring of seafood toxicity will remain as a priority for human health protection, a better understanding of toxin accumulation and detoxification dynamics might allow for forecasting tools to design better cost-effective mitigation strategies for bivalve farming and fisheries. In this study we explore monitoring data to extract temporal trends in natural accumulation and detoxification of paralytic shellfish poison (PSP) for two important mytilids from the Northwest Patagonian inland sea: Mytilus chilensis and Aulacomya atra. The data were collected between 1995 and 1998 in 13 stations, during two Alexandrium catenella blooms. The generalized linear models approach applied indicated A. catenella concentration, exposure time, salinity, temperature and zone had significant effects upon PSP concentration during the accumulation phase. Time, salinity, temperature and zone had significant effects upon PSP concentration during the detoxification phase. To obtain quantitative descriptors for accumulation and detoxification dynamics, we construct a simplified one-box model, defined by two parameters: 1) the proportionality constant between A. catenella concentration and PSP and 2) the instantaneous PSP decay rate. In spite of the limited nature of available data, the proposed model described significantly the observed variation in accumulation and detoxification trends of PSP. It remains. However, an evident need to validate the model against independent data sets from the same area and to identify and quantify sources of variability, uncertainty and bias that may affect model parameters.La acumulación de toxinas marinas en filtradores implica serios riesgos a la salud humana y pérdidas económicas. Mientras que el monitoreo directo de la toxicidad de los mariscos permanecerá como una prioridad para proteger la salud humana, la comprensión de la dinámica de acumulación y detoxificación permitiría desarrollar herramientas predictivas para diseñar estrategias de mitigación para la acuicultura y pesca. En este trabajo se estudiaron patrones temporales de acumulación y detoxificación de veneno paralizante de los mariscos (VPM) en dos mitilidos de importancia comercial en el mar interior de la Patagonia Noroccidental: Mytilus chilensis y Aulacomya atra. Se utilizaron datos de monitoreo, entre 1995 y 1998 recolectados en 13 estaciones durante dos florecimientos de Alexandrium catenella. Aplicando modelos lineales generalizados se observó que la concentración de A. catenella, tiempo de exposición, salinidad, temperatura y zona, afectaron la concentración de VPM durante la fase de acumulación. Tiempo, salinidad, temperatura y zona afectaron la concentración de VPM durante la fase de detoxificación. La dinámica de acumulación y detoxificación de VPM se estudió a través de un modelo de una caja definido por dos parámetros, 1) el coeficiente de proporcionalidad entre A. catenella y VPM y 2) la tasa instantánea de decaimiento de la toxina. A pesar de las limitaciones del los datos utilizados, el modelo logró explicar una fracción significativa de la variación observada en la acumulación y detoxificación de VPM. Sin embargo es necesario validar este modelo contra un set de datos independientes del área de estudio e identificar y cuantificar fuentes de variabilidad, incerteza y sesgo que afecten sus parámetros

Occurrence and Abundance of an Apex Predator and a Sympatric Mesopredator in Rural Areas of the Coastal Range of Southern Chile

The two mammalian carnivores, puma (Puma concolor) and South American grey fox (Lycalopex griseus) were studied, in a remote area located in the humid temperate forest of the coastal range of southern Chile. A total of six locations were selected in three landscapes: pre-mountain range, mountain range, and coast. The chosen study locations are relevant because they correspond to threatened areas with different levels of human intervention., so they offer the ideal setting for studying how different species of carnivores respond to both human presence and activities. A dataset was collected for 24 months during 2016–2018 through photo-trapping (13 camera traps placed along 50 photo-trap stations). Wes estimated the apparent occurrence and relative abundance index (RAI) of the fauna registered, by means of generalized linear models to contrast those of an apex predator, such as the puma and a sympatric mesopredator, the South American grey fox, across the three landscapes. The ecological variables assessed were the RAI of the other carnivore considered, exotic carnivores such as dogs and cats, human intervention, farmland effect, prey availability, and habitat quality. The primary hypothesis was that the apparent occurrence and RAI of puma and fox would be positively associated with the RAI of prey and livestock and negatively with human intervention. On the other hand, the secondary hypothesis dealt with the interactions between puma and fox faced with different degrees of human intervention. The results showed that the apparent occurrence of the puma was statistically explained by location only, and it was highest at the mountain range. The apparent occurrence of foxes was explained by both puma apparent occurrence and relative integrated anthropization index (INRA), being highest in the pre-mountain range. Concerning the RAI of pumas, high values were yielded by location and fox RAI. For the RAI of foxes, they were location, puma RAI, and INRA. It can be suggested that eucalyptus plantations from the pre-mountain range could offer an adequate habitat for the puma and the fox, but not the coastal range, as the mountain range could be acting as a biological barrier. Due to the nature of the data, it was not possible to detect any relevant effect between the two carnivores’ considered, between their respective preys, or the very abundant presence of dogs