Anisakid nematodes in thread herrings from the Gulf of California: food safety considerations and spatial patterns in parasite assemblages.

The 13 California sea lion breeding colonies in the Gulf of California (GoC), Mexico are each characterized by different population growth trends, including a variable number of births. Despite being located in a highly productive marine area, both the species’ population and the number of births have declined significantly over the past few decades. The goal of this study was to assess the effects of certain environmental variables on the number of births at colonies in three regions (northern, central and southern) of the GoC (1995–2018). Data on diet, small pelagic fish catches by fisheries, the density of small pelagic fish schools, remotely sampled values of sea surface temperature and chlorophyll‐a concentration and El Niño Southern Oscillation events were collected in order to evaluate whether these variables had an effect on the number of births using correlations and generalized linear models. No significant relationships were found between the environmental variables and the number of births. However, the number of births decreased when the sea surface temperature anomalies exceeded 1°C in the northern and central regions of the GoC. Although no significant relationships were found between the small pelagic fish catches and the number of births, positive trends were observed between sardine catches and the number of births during certain periods in the central region. A positive correlation between the density of small pelagic fish schools and the number of births suggests a possible relationship between prey availability and reproductive success in the central region. A Programme of Action for the Conservation of the Species should be promoted by the Federal Government and carried out in order to implement specific management actions. Specifically, surveillance efforts should increase, fishing gear conversion plans should be established and sea lion exclusion devices should be introduced, among other measures.

Abstract: Near-surface distribution (10–40 m depth), abundance, and biomass of small pelagic fish were estimated using an echo sounder (EY-60, 120 kHz) during January 2007 in central and northern areas of the Gulf of California. Small pelagic fish distribution was spatially correlated with simultaneous, continuous, high-resolution measurements of 4 m depth temperature, salinity, turbidity, chlorophyll a, and dissolved oxygen concentration to characterize water and habitat conditions. Small pelagic fish shoals were concentrated in five areas of northern and central parts of the gulf, along the coast of Sonora, and south of Isla Tiburon. About 62% of small pelagic fish abundance and 57% of the biomass was echo-detected during the night, when small pelagic fish tend to assemble near the surface. Fish abundance in these areas (11,210 km2) was estimated at 6.16 ×109 individuals. Echo-integrated median biomass was 2.6 ×105t. Projecting this biomass to the surveyed area (80,102 km2), median biomass of multispeci...

In the Gulf of California, small pelagic fish like sardines, anchovies and mackerels are of ecological and economic importance. A particular feature of these species is their tendency to form schools, which can be described by their size, acoustic density, position and location in the water column. The aim of this work was to analyse the characteristics of the Gulf of California small pelagic schools and their dynamics in the water column in two different seasons during the same year. The information from two acoustic surveys was obtained with a scientific echosounder SIMRAD EK60 (split beam, 38 kHz) during the winter (February) and spring (May and June) 2014. To analyse the degree of grouping in the schools, echo-integration by shoal was done using Movies+ post-processing software, obtaining variables corresponding to morphological, energetic and bathymetric aspects of the detected schools. The analysis allowed the recognition of 301 acoustic schools, the majority of which (81 %) were observed during winter, while 67 % were detected at night, and 23 % during twilight periods. Spring schools showed higher mean volume backscattering strength (S v , dB re 1 m−1) and a more compact morphology (lower length, height and area) compared to winter detections; only during night-time similar conditions of acoustic energy and morphology were observed in both seasons. The school vertical distribution in winter was similar to that commonly reported for small pelagic fish for other regions, where a great number of schools is observed at depth during the day. Winter detections were also observed at greater depths. On the other hand, during the spring, the diurnal schools showed higher values of S v , nevertheless, in this season there seems to be no day and night differences between vertical distribution of the schools.

The first steps have been taken to analyze the effects of small pelagic harvests on the Gulf of California ecosystem. The primary goal of this study was to estimate the latitudinal differences in regionalized baselines of endangered and threatened marine species attracted to a purse seine in a Mexican fishery of small pelagic fish. We also analyzed the spatial patterns in fishing effort in the Gulf of California. Seven zones were analyzed in the Gulf of California, including the east and west coasts, and a total of 3,051 fishing sets were analyzed during January 2013 and July 2014; the data provided a comprehensive picture of the distribution of the fishing effort, small pelagic fishes harvested, and the presence of species attracted to the fishing sets. The region in the upper Gulf of California showed a low presence of individuals, and the east coast recorded more sightings than the west coast; consequently the fishing effort was mainly distributed in the east coast. The number of individuals for several species sighted and counted by fishing set was used for each zone in the Gulf of California, and a conservative baseline based on the Pennington estimator was computed. It provided an average value of endangered and threatened marine species attracted to a purse seine for each zone. The Pennington estimator is recommended due to the precision of the confidence intervals and the nature of the uncertainty in the data collection based on sightings.

Anisakid nematodes in Trichiurus lepturus and Saurida undosquamis (Teleostea) from the South-West Indian Ocean: Genetic evidence for the existence of sister species within Anisakis typica (s.l.), and food-safety considerations

Background: The Pacific sardine is a small pelagic fish which supports the most important fishery at national scale. Goals: This paper analyzes the catch information generated by the commercial fleet operating in the Gulf of California from 1969 to 2016 in order to identify the catch trends and the presence of the harmonic components that is related to environmental variability. Methods: Fast Fourier Transformation (FFT) was applied to the time series in order to establish the dominant frequencies. The Singular Spectrum Analysis (SSA) method was used to separate the trend and harmonic components. Each harmonic component was correlated to the Southern Oscillation Index (SOI), the Pacific Decadal Oscillation (PDO) and the Solar Activity data. Results: The FFT showed dominant frequencies at 7 and 11 years. An increasing linear trend was identified from 1969 to 2008 with a decreasing linear segment from 2009 to 2016, as well as two harmonic components of different frequencies (7 and 11 years respectively). The trend and the two harmonic components explain 87.49% of the total variance of the capture. The first and second harmonic components correlated positively with SOI (r= 0.2921, r= 0.3870 respectively), while the second harmonic component correlated negatively with solar activity (r= -0.5313). There were no correlations with the PDO. Conclusions: The fluctuations of Pacific sardine in the Gulf of California are mainly due to three factors: increased catch, the influence of the El Niño events and the influence of the solar activity cycle.  

The feeding habits of the Panama brief squid, Lolliguncula panamensis (Berry, 1911), it inhabits off Peru until Gulf of California, was determined by examining the stomach contents of 657. Panama brief squid were collected from the incidental catch of shrimp trawling fishery during 2003-2006 and 2008, along the Gulf of California, Mexico. Most of the stomachs were empty and those that contained food presented highly digested prey items. Eight taxa were identified in the stomach contents and the index of relative importance indicated to juvenile of Pacific sardine (Sardinops sagax), the most important prey, this prey bring 99.6% IRI. Results suggest that L. panamensis is a highly opportunistic predator foraged primarily in coastal and epipelagic waters, whose diet reflect the local abundance of potential prey species, mainly small pelagic fishes.

Small pelagic fishes (e.g., sardines, anchovies and their relatives) are preyed upon by large predatory fishes, birds and mammals, and thus, are key species in marine food webs and with respect to ecosystem health and productivity. However, we know little about their physiology, and such information will be critical to predicting how their populations may be impacted by human-induced rapid environmental change (HIREC) and in implementing effective conservation strategies. As a first step, we determined the maximum swimming speed, aerobic capacity [maximum metabolic rate (MMR) and aerobic scope (AS)] and cost of transport (COT; the energy required to swim a given distance) of scaled sardines (Harengula jaguana) collected in Eleuthera (The Bahamas). The scaled sardine’s critical swimming speed (Ucrit) was ~ 5–6 body length’s per second, and this agrees with data collected on free-swimming schools of similar fishes in the wild. However, they had unexpectedly high values for MMR and AS (~ 25% and 70% greater than tuna, respectively), and for COT. These findings have important implications with regard to how these ecologically important fishes will potentially respond to HIREC-related challenges such as increased temperature and decreases in the biomass and size of plankton upon which they feed.

Long-term hydrographic changes in the Gulf of California and ecological impacts: A crack in the World’s Aquarium?

Intra-isolate heterogeneity of the ITS region of rDNA in Pythium helicoides

A probabilistic procedure for estimating an optimal echo-integration threshold using the Expectation-Maximisation algorithm

Background: The Pacific sardine is a small pelagic fish which supports the most important fishery at national scale. Goals: This paper analyzes the catch information generated by the commercial fleet operating in the Gulf of California from 1969 to 2016 in order to identify the catch trends and the presence of the harmonic components that is related to environmental variability. Methods: Fast Fourier Transformation (FFT) was applied to the time series in order to establish the dominant frequencies. The Singular Spectrum Analysis (SSA) method was used to separate the trend and harmonic components. Each harmonic component was correlated to the Southern Oscillation Index (SOI), the Pacific Decadal Oscillation (PDO) and the Solar Activity data. Results: The FFT showed dominant frequencies at 7 and 11 years. An increasing linear trend was identified from 1969 to 2008 with a decreasing linear segment from 2009 to 2016, as well as two harmonic components of different frequencies (7 and 11 years respectively). The trend and the two harmonic components explain 87.49% of the total variance of the capture. The first and second harmonic components correlated positively with SOI (r= 0.2921, r= 0.3870 respectively), while the second harmonic component correlated negatively with solar activity (r= -0.5313). There were no correlations with the PDO. Conclusions: The fluctuations of Pacific sardine in the Gulf of California are mainly due to three factors: increased catch, the influence of the El Niño events and the influence of the solar activity cycle. &nbsp

The Gulf of California: Review of ecosystem status and sustainability challenges

Environmental status of the Gulf of California: A review of responses to climate change and climate variability

Small pelagic fishes occupy an important trophic role in every global aquatic ecosystem, and many species are heavily exploited by fisheries, including some of the largest and most valuable capture fisheries in the world. In November 2022, a symposium on small pelagic fish titled “ Small Pelagic Fish: New Frontiers in Science and Sustainable Management” was cohosted by PICES, ICES, and FAO in Lisbon, Portugal. This special issue contains a collection of research manuscripts that explore approaches currently being used and developed to assess and manage small pelagic fishes. In particular, this issue covers topics on novel approaches to surveying small pelagic fishes, incorporating environmental covariates into management, management strategy evaluation, and aspects of the economics of small pelagic fisheries. The conclusions highlight the importance of new approaches that seek to enhance small pelagic fish surveys and ecosystem monitoring, incorporate that ecosystem information into management strategy evaluation, and predict the potential impacts of ecosystem changes on outcomes for economies and communities that rely on sustainable populations of small pelagic fishes.