Sardinops Research Articles

Concentrations and relative compositions of metallic elements differ between predatory squid and filter-feeding sardine from the Indian and South Atlantic oceans

Although metallic elements occur naturally, they can occur or accumulate in organisms at levels toxic to the organism and/or their consumers. Concentrations of twenty-nine metallic elements in muscle tissue from sardine Sardinops sagax and chokka squid Loligo reynaudii from South Atlantic and Indian Ocean waters off South Africa were established, for the first time, using inductively-coupled plasma mass spectrometry. Chokka showed significantly higher (p < 0.05) concentrations of B, Cr, Zn, As, Se, Rb, Sr, Cd, and Tl and significantly lower concentrations of V, Mn, Ti, and Mo compared to sardine. There were also significant differences in some metallic elements between the two oceans. Multivariate analyses indicated possible population structure of both species, suggesting that these analyses may be useful as a stock discrimination tool. Only two sardine samples contained quantifiable Hg. Based on South African estimated daily intake, total hazard quotient, and European Union limits for Hg, Cd, and Pb, we consider tissues from sardine and chokka in South African waters to be safe for human consumption.

Metabolic measurements and parameter estimations for bioenergetics modelling of Pacific Chub Mackerel Scomber japonicus

AbstractAs a crucial step in developing a bioenergetics model for Pacific Chub Mackerel Scomber japonicus (hereafter chub mackerel), parameters related to metabolism, the largest dissipation term in bioenergetics modelling, were estimated. Swimming energetics and metabolic data for nine chub mackerel were collected at 14°C, a low temperature within the typical thermal range of this species, using variable‐speed swim‐tunnel respirometry. These new data were combined with previous speed‐dependent metabolic data at 18 and 24°C and single‐speed (1 fork length per second: FL/s) metabolic data at 15 and 20°C to estimate respiration parameters for model development. Based on the combined data, the optimal swimming speed (the swimming speed with the minimum cost of transport, Uopt) was 42.5 cm/s (1.5–3.0 FL/s or 2.1 ± 0.4 FL/s) and showed no significant dependence on temperature or fish size. The daily mass‐specific oxygen consumption rate (R, g O2 g fish−1 day−1) was expressed as a function of fish mass (W), temperature (T) and swimming speed (U): R = 0.0103W−0.490 e(0.0457T) e(0.0235U). Compared to other small pelagic fishes such as Pacific Herring Clupea harengus pallasii, Pacific Sardine Sardinops sagax and various anchovy species, chub mackerel respiration showed a lower dependence on fish mass, temperature and swimming speed, suggesting a greater swimming ability and lower sensitivity to environmental temperature variation.

Disentangling the effects of climate and density-dependent factors on spatiotemporal dynamics of Japanese sardine spawning

Disentangling the effects of climate and density-dependent factors on spatiotemporal dynamics of Japanese sardine spawning

A snapshot assessment of the diet of Cape fur seals Arctocephalus pusillus pusillus at Ilha dos Tigres, Angola

The population of Cape fur seal Arctocephalus pusillus pusillus at Ilha dos Tigres off the coast of southern Angola is expanding. Until now the only available biological information on the population has been its demographic parameters, and this insufficiency has hindered our understanding of the population’s ecology. The current study aimed to describe the diet of this northernmost population of the subspecies, based on a once-off sampling opportunity. The diet was described using scat analysis and hard-part identification from scats collected in July 2014. Small pelagic fishes (Trachurus spp., Engraulis encrasicolus and Sardinops sagax) were the numerically dominant prey items, conforming with the findings of studies conducted on other Cape fur seal colonies. Although not numerically dominant, cephalopods were dominant in terms of mass.

Influence of wind events on larval fish mortality rates in the southern California Current Ecosystem

Wind-induced mixing can affect the vertical distribution of plankton in the upper water column, influencing the prey available for larval fishes. The stable ocean hypothesis proposes that periods of calm winds facilitate the development of plankton layers at concentrations sufficient for successful larval foraging and increased survival. Conversely, storm events redistribute prey, leading to reduced foraging success. Here, we investigate this hypothesis by comparing larval fish mortality rates estimated from 37 years of ichthyoplankton data against metrics of wind events defined as storms and calm periods. Contrary to expectations, we found that mortality for Pacific hake (Merluccius productus) significantly decreased as storm events increased in the southern California Current Ecosystem. Mortality rates for northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), Pacific mackerel (Scomber japonicus), and jack mackerel (Trachurus symmetricus) had no relationship to storms, and no species’ mortality rates were related to the number of calm events. Our results highlight the differing sensitivities of larval survival among fishes in the region and indicate that responses to atmospheric processes are species-dependent.

Ecosystem-based management can contribute to cooperation in transboundary fisheries: The case of pacific sardine

Transboundary fish stocks complicate sustainable fishing strategies, particularly when stakeholders have diverse objectives and regulatory and governance frameworks. Pacific sardine (Sardinops sagax) in the California Current is shared by up to three fishing nations— Canada, the United States, and Mexico—and climate-driven abundance and distribution dynamics can complicate cooperative fisheries, leading to overfishing. This study builds on previous analyses by integrating ecosystem linkages into a game theory model of transboundary sardine fisheries under various climate scenarios. Cooperative fishing strategies that account for the ecosystem-wide value of sardine as forage for other species result in increased economic benefits compared to strategies that only account for the single-species value of sardine fisheries to a given fishing country. Total ecosystem landed value is maximized at a sardine fishing rate only somewhat lower than sardine FMSY, which is more precautionary but still allows the fishery to operate. Incorporating ecosystem dynamics into management-applicable models can highlight ways in which ecosystem-based fisheries management can improve both sustainability and profitability and help managers prioritize wider ecological research. Ecosystem-based management will be increasingly required to understand and adapt to the observed rapid shifts in species distributions due to climate change, and to design strategies to achieve sustainable and profitable fisheries amidst changing ecosystems.

Prevalence of Kudoa thyrsites (Myxozoa) in South African sardine Sardinops sagax, kingklip Genypterus capensis, and Cape hakes Merluccius capensis and M. paradoxus

Prevalence of infection with the myxozoan parasite Kudoa thyrsites is not well documented in sardine Sardinops sagax, the Cape hakes Merluccius capensis and M. paradoxus, and kingklip Genypterus capensis. Quantitative polymerase chain reaction assays were used to determine the prevalence of K. thyrsites in wild-caught S. sagax (n = 296), Merluccius spp. (n = 162) and G. capensis (n = 70), harvested in 2015. Sardinops sagax were harvested from the east, south and west coasts of South Africa, whereas M. capensis, M. paradoxus and G. capensis were taken from the west coast only. Relationships between K. thyrsites infection prevalence and fish capture locality, season, sex and size were determined with Chi-square tests. Prevalence was highest in S. sagax (91%), followed by M. capensis and M. paradoxus (87%) and G. capensis (40%). Prevalence was independent of sex of the host for all fish species. In the case of S. sagax only, the prevalence of infection was independent of locality of capture but depended on season, with prevalence lowest during spring and highest during autumn. No significant relationship (p > 0.05) was found between infection prevalence and host size for any of the fish species.

Interannual Dynamics of the Fish Community’s Integral Characteristics in the Upper Epipelagic Layer of the Pacific Ocean’s Russian Part in June–September 2004–2018

Interannual dynamics of the integral characteristics of species structure in the fish community in the Pacific waters off the Kuril Islands in 2004–2018 is described. During that period, the species richness of the fish community was relatively low: 88 fish and fishlike species (annual average 41.06 ± 1.55) of three classes, 20 orders, 47 families, and 75 genera. It was revealed that species diversity and evenness of species structure are decreased because of subtropical species' mass migrations (chub mackerel Scomber japonicus and Japanese sardine Sardinops melanostictus) to the region in the warm season. Changes in the species structure of ichthyocene occurred in 2013–2014. The values of Simpson dominance index (from 4.85 ± 0.44 to 2.97 ± 0.29) and Pielou evenness species structure (from 0.41 ± 0.04 to 0.21 ± 0.03) decreased, while the measure of the concentration of species richness (Margalef index) did not significantly change (3.43 ± 0.14 on average). The hypothesis of the “Japanese sardine’s Epoch” onset is discussed.

Use of parasites to clarify residency and migration patterns of Pacific sardine (Sardinops sagax) in the California Current

Use of parasites to clarify residency and migration patterns of Pacific sardine (Sardinops sagax) in the California Current

Zoonotic nematode parasites infecting selected edible fish in New South Wales, Australia

Despite increases in the annual consumption of seafood in Australia, studies on the occurrence and prevalence of zoonotic parasites in fish and the risk they may pose to human health are limited. The present study was aimed at determining the occurrence of zoonotic nematodes in commonly consumed fish in New South Wales, Australia's most populous state. Three species of fish, including the Australian pilchard, Australian anchovy, and eastern school whiting, were purchased from a fish market and examined for the presence of nematode parasites. All Australian pilchards examined in this study were infected (100%; n = 19), followed by the eastern school whiting (70%; n = 20) and Australian anchovy (56%; n = 70). Nematodes were in the larval stage and, therefore, classified by morphotype, followed by specific identification through sequencing of their internal transcribed spacer (ITS) regions. Seven different larval types with zoonotic potential, belonging to the families Anisakidae (Contracaecum type II and Terranova type II) and Raphidascarididae (Hysterothylacium types IV [genotypes A and B], VIII, XIV and a novel Hysterothylacium larval type, herein assigned as type XVIII), were found. The new larval type was identified as Hysterothylacium thalassini, based on ITS sequence data. The presence of the infective stage of a range of zoonotic parasites in fish commonly consumed in New South Wales is important, particularly as, in some dishes, these fish are used whole, raw or undercooked. This study provides the basis for future research on other aspects of these parasites, in regards to public health.

Length conversions and mass-length relationships of five forage-fish species in the California current ecosystem.

Length-measurement conversions and seasonal mass-length relationships (MLR) for Pacific herring Clupea pallasii, northern anchovy Engraulis mordax, Pacific sardine Sardinops sagax, Pacific mackerel Scomber japonicus and jack mackerel Trachurus symmetricus in the California Current are presented. The conversions between total (LT ), fork (LF ,) and standard lengths (LS ) should facilitate comparisons of data across disciplines and institutions. These equations resulted from an analysis of measurements spanning 14 years and the western seaboard of North America, from the north end of Vancouver Island to the USA-Mexico border. Major-axis regressions were used to calculate reciprocal length-measurement conversions (e.g., LT to LS and LS to LT ) and generalised linear models and ordinary least-squares models were used to create MLRs that account for seasonal variations. The MLR models indicated seasonal differences for all species except C. pallasii, for which there was no multi-season data. Discrepancies between these and published models were examined, along with the suitability and benefit of the various types of models used for length-measurement conversion and MLRs.

Potential changes in the distribution of suitable habitat for Pacific sardine (Sardinops sagax) under climate change scenarios

The Pacific sardine, Sardinops sagax, is the most important fishery by volume in Mexico; however, this small pelagic species shows fluctuations in catch due to its susceptibility to environmental changes. In turn, this susceptibility leads to variations in distribution, abundance, and recruitment, making the Pacific sardine highly vulnerable to the effects of global climate change. In this study, we analyze the effects of environmental variability on the Pacific sardine distribution through the development of the habitat suitability for the Mexican Pacific. We used bathymetry, sea surface temperature (SST), sea surface salinity (SSS) and net primary productivity (NPP) to develop an ecological niche model to forecast the suitable habitat of the Pacific sardine and reproduce the historical patterns for the 2003–2017 period. We then used this model to make future projections to the year 2100 using the emission scenarios RCP 2.6, 4.5, and 8.5 proposed by the Intergovernmental Panel on Climate Change. Under the RCP models, on average, the greatest impact of climate change was observed inside the Gulf of California, with an increase in SST (+1.68 °C) and a decrease in 25% of NPP (−256 mg C m−2 d−1) reducing habitat availability for this species by 95. Stocks on the Pacific coast are projected to fluctuate substantially, similar to past events driven by environmental variability. At the regional level, a loss of suitable habitat of up to 50% is expected by the end of this century for the Pacific sardine.

Análisis de la serie de captura de sardina Monterrey, Sardinops sagax en el Golfo de California, México

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;

Análisis de la serie de captura de sardina Monterrey, Sardinops sagax en el Golfo de California, México

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;

Spermatophore production and sperm quality of the river prawn Macrobrachium americanum Spence Bate, 1868 fed with different diets

The effects of different diets on spermatophore production and sperm quality were investigated in the river prawn Macrobrachium americanum. River prawns were cultured and fed with three diets for 244 days: fresh food (50% squid meat, Dosidicus gigas and 50% sardine muscle, Sardinops sagax); commercial pellets (35 Purina®); and a 50:50 mixture of both diets. Spermatophore production was recorded every 24 days on average as the percentage of spermatophores produced per extraction per diet, weight and biochemical composition. Sperm quality was measured as the total number of sperm, the proportion of live/dead sperm and normal/abnormal sperm morphology. There were no significant differences in the mean biochemical composition of M. americanum spermatophores for any of the diets. Biochemical composition was 36.3% protein, 25.8% carbohydrate and 4.6% lipids for all data pooled. The weight of spermatophores and sperm counts was not significantly different among diets, nor were there any differences as a function of the male initial total length (p > .05). Male river prawn reproductive exhaustion was observed as a decline in spermatophore production, weight of the spermatophores and the number of sperm cells per spermatophore, with an increasing proportion of dead and abnormal sperm seen throughout the experiment. The recommended period of maintenance in captivity for male broodstock is less than 115 days. It is recommended to feed broodstock males of M. americanum with commercial pellets because no significant differences were detected with the diets tested; pellets are easier to use, ensuring the same spermatophore production and sperm quality that was obtained with fresh food.

Fish larvae as indicator species of interannual environmental variability in a subtropical transition area off the Baja California peninsula

The aim of this work was to determine if the variation patterns in the abundance of dominant species of fish larvae in the transition zone off Bahía Sebastián Vizcaíno, Mexico, could be used as indicators of interannual environmental variability, and how larval fish assemblages respond to this environmental variability during the period 1997–2013. With the 16 years of plankton data in the southern region of the California Current System, anomaly curves of larval abundance were calculated, from which the temporal abundance patterns of the dominant fish larvae of the mesopelagic, epipelagic and demersal environments were obtained. Classification and ordination analyses were carried out to obtain the larval fish assemblages as well as their relations with environmental variables (sea surface temperature, surface salinity, concentration of Chlorophyll-a and zooplanktonic volume) and climatic indexes (ONI, MEI, PDO and NPGO). Results showed a high positive correlation between the mesopelagic abundance with MEI and PDO indices, demonstrating their affinity with warm oceanic waters, while there were not statistically significant correlation between the climatic indexes and the epipelagic (Sardinops sagax and Engraulis mordax) or demersal species (Synodus lucioceps). The interannual variability of the abundance of three dominant mesopelagic species (Vinciguerria lucetia, Diogenichthys laternatus and Cyclothone signata) show that these species had a clearer response to environmental variability than epipelagic and demersal species. Trends in the abundance of mesopelagic species larvae and their high correlation values with the environmental variables used, demonstrate their potential as indicators of environmental change of the pelagic ecosystem in the transitional area off Bahía Sebastián Vizcaíno.

Integration of sonar and optical camera images using deep neural network for fish monitoring

Fish monitoring in aquaculture farms is indispensable for managing the growth and health status of fish resources. However, it is unrealistic to expect humans to be able to perform monitoring at night, when standard optical cameras are generally inapplicable. Although sonar systems can be used at night, their practical applications are limited by their monochrome, low-quality images. In this paper, we describe a realistic image generation system that uses sonar and camera images recorded at night. The proposed approach is based on conditional generative adversarial networks, which learn the image-to-image translation between sonar and optical images. We tested the system in a fish tank containing thousands of sardines (Sardinops melanostictus). Images were simultaneously recorded using high-precision imaging sonar and an underwater camera. Experimental results show that the proposed model successfully generates realistic daytime images from sonar and night camera images. Our system enables nighttime monitoring using sonar and an optical camera, leading to more efficient fish farming and environmental surveillance.

Establishing genome sizes of focal fishery and aquaculture species along Baja California, Mexico

Genome size—the total haploid content of nuclear DNA— is constant in all cells in individuals within a species, but differs among species. Consequently, the genome size is a quantifiable genetic signature that not only characterizes a species, but it can reflect chromatin modifications, which play fundamental roles in most biological processes that are involved in the manipulation and expression of DNA. This characteristic makes the genome size a crucial parameter for genetic research on endemic aquatic species and for genetic manipulations in aquaculture species. Technologies for genetic assessments and improvements applied to fishery and aquaculture species use genome size values as a means by which hybrids, polyploids, and sex can be identified, when sex chromosomes exist. The objectives of this study were to determine genome sizes of aquatic species with economic and biological importance along the Pacific coast of Mexico, as well as to identify the appropriate reference standards for use in this study. Blood, hemolymph or milt were collected from 10 species occurring along the coast of Baja California: Sablefish Anoplopoma fimbria, Black Snapper Lutjanus novemfasciatus, California Halibut Paralichthys californicus, Pacific Sardine Sardinops sagax, Flag Rockfish Sebastes rubrivinctus, Starry Rockfish Sebastes constellatus, Totoaba Totoaba macdonaldi, Whiteleg Shrimp Litopenaeus vannamei and two Yellowtail Seriola lalandi and S. dorsalis. Nuclear DNA was stained with propidium iodide solution and the genome size was determined by flow cytometry, with results ranging from 0.61 pg (1.22 pg/diploid cell) to 2.59 pg (5.18 pg/diploid cell), with the smallest value in Sablefish and the largest in the Whiteleg Shrimp. No significant differences were detected (P ≤ 0.05) among individuals of the same species; the likely reason behind any dissimilar DNA content values with those from the literature were differences in methodologies or variations in genetics. Red-ear Slider Turtle Trachemys scripta elegans 2.65 pg (5.30 pg/diploid cell) and Red Junglefowl Gallus gallus 1.27 pg (2.54 pg/diploid cell) were chosen as the standards for reference values. These results establish the basis for the Mexican National Aquatic Genetic Resources project supporting genetic improvements for aquaculture and conservation status parameters for fisheries species.

Profit and equity trade‐offs in the management of small pelagic fisheries: the case of the Japanese sardine fishery*

The management of small pelagic fisheries is difficult due to environmental regime changes that generate multi‐decadal cyclic fluctuations in stock abundance. Lagged management responses to environmental factors can amplify the effects of fishing and may even result in stock collapse. In this paper, we develop an age‐structured bioeconomic model to explore the effectiveness of alternative management approaches for cyclically fluctuating small pelagic fish stocks. The fishery outcomes are evaluated against the overall profit of the fishery and the intertemporal distribution of fishing profits. The model is parameterised for the Japanese sardine fishery, once the largest fishery in Japan, which has experienced a prolonged period of stock collapse over the last 100 years. The results show that the duration of fishery collapse is mostly determined by the extent of cyclic fluctuations in the recruitment of immature sardines, but the effects of the fluctuations on the fishery are heightened by the cumulative impact of fishing. We further show that restricting fishing reduces the fishery’s overall profits, but smooths the intertemporal distribution of profits, resulting in greater intergenerational equity. This income smoothing effect is particularly pronounced when the stock exhibits high levels of cyclic fluctuations.

Disentangling density‐dependent effects on egg production and survival from egg to recruitment in fish

AbstractUnderstanding of density‐dependent effects is key to achieving sustainable management of self‐regulating biological resources such as fish stocks. Traditionally, density‐dependent effects on population abundance in fish have been considered to occur from hatching to recruitment, based on the paradigm of proportionality between spawning stock biomass and total egg production. Here, we demonstrate how the existence of intraspecific and interspecific density dependence in egg production changes the current understanding of density‐dependent processes in the life history of fish, by disentangling density‐dependent effects on egg production and survival from egg to recruitment, using sardine (Sardinops melanostictus, Clupeidae) and anchovy (Engraulis japonicus, Engraulidae) as model species. For sardine, strong intraspecific density‐dependent effects occurred in egg production, but no density‐dependent effects occurred or if any they were weak enough to be masked by environmental factors from hatching to recruitment. In contrast, for anchovy, interspecific density‐dependent effects occurred in egg production. In the survival after hatching, anchovy experienced stronger intraspecific density‐dependent effects than currently recognized. This analysis could overturn the current understanding of density‐dependent effects in the life history, highlighting contrasts between the effects on individual quality and population abundance and between the model species. We propose to reconsider the basis of fisheries management and recruitment studies based on the revised understanding of density‐dependent effects in the life history of the respective species.