Uso de morfometría geométrica para la identificación de variaciones ecofenotípicas en juveniles de esturión persa Acipenser persicus

Study of phenotypic variation is essential for identifying discrete phenotypic stocks. We sampled immature Persian sturgeon from the eastern and western portion of the southern Caspian Sea to test for morphological differences that could predict the ecophenotypic variation of Persian sturgeon. Geometric morphometric methods were used to quantify body shape. Configuration of landmark coordinates of fish body were scaled, translated and rotated using generalized Procrustes analysis, followed by univariate analysis of variance of resulting shape coordinates to evaluate potential morphological differences between regions. A principal component analysis was carried out to reduce the number of dimensions without the loss of information. The discriminate function analysis was performed to determine the efficacy of body landmarks for discrimination by geographic variants. Within-group linkage was inferred for dendrogram clusters using Pearson correlation distance on the basis of the average linkage method as a complement for discriminate analysis. Principle component analysis revealed that the largest differences were in body size. Most notable were differences in distance between head landmarks and the dorsal fin between eastern and western regions. Fish from the western region exhibited a longer distance from head landmarks to the dorsal fin than fish from the eastern region. Furthermore, the ventral portion of fish from the western region was longer than that of the eastern individuals. These findings show that juvenile Persian sturgeon already possess morphological traits that can be used to discriminate fish from different regions. Furthermore, these differences are discernible in spite of the volume of artificially-inseminated sturgeon larva that have been released during the past 40 years.El estudio de la variación fenotípica es esencial para la identificación de estirpes fenotípicas concretas. Con el fin de identificar diferencias morfológicas que permitan predecir variaciones eco-fenotípicas en el esturión persa, individuos inmaduros de esta especie se muestrearon en diferentes regiones del este y el oeste del sur del mar Caspio. Se utilizaron métodos morfométricos geométricos para cuantificar la forma del cuerpo. La configuración de coordenadas referenciadas del cuerpo del pez fueron escaladas, trasladadas y rotadas utilizando el análisis generalizado Procrustes, seguido del análisis Univariante de la Varianza de las coordenadas de forma resultantes, con el fin de evaluar posibles diferencias morfológicas entre diferentes zonas. Se utilizó un análisis de componentes principales para reducir el número de dimensiones sin perder información. Los scores de los componentes del cuerpo se sometieron a análisis discriminante, con el objeto de determinar la eficacia de las coordenadas referenciadas en la discriminación de las variantes geográficas. Las relaciones entre grupos para clusters de dendrograma se infirieron usando la correlación de distancias de Pearson, tomando como base el método de relación media como complemento del análisis discriminante. El análisis de componentes principales reveló que las mayores distancias fueron en la talla. Destacaron las diferencias encontradas en la distancia entre las referencias de cabeza y aleta dorsal entre las regiones del Este y Oeste. La distancia relativa entre las referencias de cabeza y aleta dorsal fue mayor en los peces de la región Oeste que en los de la región Este. Además, la porción ventral de los peces de la región Oeste fue mayor que la de los individuos del Este. Estos resultados indican que los juveniles de esturión persa ya muestran características morfológicas que pueden utilizarse para la discriminación de individuos de diferentes regiones. Además, estas diferencias son discernibles a pesar de la cantidad de larvas de esturión que, obtenidas por inseminación artificial, han sido liberadas al medio natural durante los últimos 40 años

Use of geometric morphometrics to identify ecophenotypic variation of juvenile Persian sturgeon <em>Acipenser persicus</em>

Study of phenotypic variation is essential for identifying discrete phenotypic stocks. We sampled immature Persian sturgeon from the eastern and western portion of the southern Caspian Sea to test for morphological differences that could predict the ecophenotypic variation of Persian sturgeon. Geometric morphometric methods were used to quantify body shape. Configuration of landmark coordinates of fish body were scaled, translated and rotated using generalized Procrustes analysis, followed by univariate analysis of variance of resulting shape coordinates to evaluate potential morphological differences between regions. A principal component analysis was carried out to reduce the number of dimensions without the loss of information. The discriminate function analysis was performed to determine the efficacy of body landmarks for discrimination by geographic variants. Within-group linkage was inferred for dendrogram clusters using Pearson correlation distance on the basis of the average linkage method as a complement for discriminate analysis. Principle component analysis revealed that the largest differences were in body size. Most notable were differences in distance between head landmarks and the dorsal fin between eastern and western regions. Fish from the western region exhibited a longer distance from head landmarks to the dorsal fin than fish from the eastern region. Furthermore, the ventral portion of fish from the western region was longer than that of the eastern individuals. These findings show that juvenile Persian sturgeon already possess morphological traits that can be used to discriminate fish from different regions. Furthermore, these differences are discernible in spite of the volume of artificially-inseminated sturgeon larva that have been released during the past 40 years

Determination of the Heavy Metal Bioaccumulation Patterns in Muscles of Two Species of Mullets from the Southern Caspian Sea

Although fish is a food that supplies nutrients of a high biological value, they can also be a source of some harmful substances, such as heavy metals. In the same context, some human activities in the Caspian Sea have contaminated this ecosystem during the past few years. For those reasons, our objective consisted of determining the concentrations of heavy metals and evaluating their bioaccumulation patterns in the different types of musculature in two species of mullets of commercial interest, Chelon auratus and Chelon saliens, from the southern coast of this sea. For this purpose, 20 C. auratus and 29 C. saliens were caught off this coastline and the metal concentrations in 3 different muscle locations were analyzed: the ventral, dorsal and caudal muscles of each fish. The caudal muscle had higher concentrations of Cd, Cu, Pb, and Zn, whereas As, Hg and Ni accumulation seemed to be independent of the musculature type. Overall, the Cd, Hg, and Pb concentrations exceeded the maximum levels permitted in fish by the European Union. In addition, the relationships between pairs of metals were positive and elevated in all the cases, which could be a sign of heavy metal pollution in the region sampled. Therefore, it will be necessary to continue monitoring and evaluating the degree of pollution in the Caspian Sea

Relationship Between Trace Element Content in the Brain of Bony Fish Species and Their Food Items in the Southwest of the Caspian Sea Due to Anthropogenic Activities

The trace elements (TEs) in aquatic environments due to anthropogenic activities are readily available to aquatic organisms. There are 153 fish species inhabiting the Caspian Sea. However, little is known about TE (TE) concentrations in these species. In this study, we investigated the effects of TEs levels in the brain of some bony fish species inhabiting the Caspian basin. Totally, 405 fish from nine species with different feeding behaviors including Leuciscus aspius (n = 20) and Perca fluviatilis (n = 37) as piscivores, Rutilus kutum (n = 27) and Rutilus caspius (n = 71) as carnivores, Vimba persa (n = 56), Ponticola caspia (n = 25) and Tinca tinca (n = 31) as mollusivores, and Alburnus chalcoides (n = 77) and Alosa braschnikowi (n = 61) as zooplanktivores were collected from the southwest of the Caspian Sea basin from September 2017 to June 2018. The ICP-OES was used to measure TEs in the brain tissue of fish. The variability of TEs concentrations in the brain tissues of these fishes by principal component analysis (PCA) was decreased to 63.59% and 17.68% for PC1 and PC2, respectively, exhibiting that 81.27% of the total variability is associated with K, Mg, P, S, Zn, and Al. The two-dimensional diagrams showed the weight of each component in PCA. The PC1 was mostly influenced by P, Mg, K, and Zn, while the greatest value in PC2 belonged to Al. Furthermore, the entire number of elements determined in this study was found to be a suitable indicator for the distinction between fish species based on their feeding items

Nickel and cadmium tissue bioaccumulation and blood parameters in Chelon auratus and Mugil cephalus from Anzali free zone in the south Caspian Sea (Iran) and Faro Lake (Italy): A comparative analysis

Analysis of heavy metal concentrations in fish blood is a valuable tool in environmental pollution monitoring. Among different type of fish, detritivorous fish are a very good indicator for monitoring pollution and environmental stress, along with hematological studies, which are an important indicator in eco-toxicological and biological studies

Morphometric Analyses of Phenotypic Plasticity in Habitat Use in Two Caspian Sea Mullets

To understand the functional meaning of morphological traits in the exploitation of natural resources, it is necessary to develop a quantitative, meaningful scheme for understanding ecophenotypes; this will facilitate management and conservation, which are the most pressing challenges in vulnerable aquatic environments. In this context, the management of cryptic and very similar species is more challenging, because of the difficulty of distinguishing them and determining their frequency in sympatry, even though they do not necessarily have the same ecologies. As such, in order to understand how morphological similarities are associated with their ecology, thirteen morphometric characteristics related to body landmark-based geometric morphometries, sagittal otolith morphology, and shape were examined in mature Chelon auratus and Chelon saliens, which were collected from the coastal waters of the southwest Caspian Sea between October 2020 and April 2021. Univariate and multivariate analysis of variance were conducted to evaluate the potential morphological differences between the species. The analyses highlight the morphological differences between C. auratus and C. saliens, and identify potentially helpful traits for using body and otolith shape for the interspecific distinction of these very similar species of Caspian mullet, which can reflect functional similarity and are an important component of community ecology

Plankton Community Structure and Biomass in the Eastern Middle Caspian Sea

Despite the role of planktonic organisms in the fishery value of the Caspian Sea and in addition to the increase in the plankton population in the Caspian Sea, there are few detailed studies regarding the determination of the planktonic organisms in the Caspian Sea. In the present investigation, we aimed to study the cell abundance and diversity of the phyto- and zooplankton in the eastern part of the Middle Caspian Sea in the spring of 2016. The composition of phytoplankton consisted of 50 species belonging to 4 systematic groups which were registered in the eastern part of the Middle Caspian: Cyanophyta (7), Bacillariophyta (24), Dinoflagellata (13), and Chlorophyta (6). Zooplankton were represented by 9 taxa: Cladocera—6, Copepod—1, and other groups—2. The most important phytoplankton species were Rhizosolenia calcar-avis, Anabaena bergii, Exuviaella cordata, and Binuclearia lauterbornii. The 0–50 m layer in the eastern Middle Caspian was the most productive, where the biomass varied from 98 mg/m3 to 109 mg/m3, consisting largely of diatoms. The cladoceran Evadne anonyx typica, the copepod Acartia tonsa, and the larvae of barnacle crustaceans (Cirripedia) were widely distributed in this layer. Zooplankton abundance decreased markedly with the depth. The maximum zooplankton concentrations were confined to depths down to 200 m