Length–weight relationships and growth parameters of two endemic fish species (Floridichthys polyommus Hubbs, 1936 and Fundulus persimilis Miller, 1955) from the Yucatan Peninsula,Mexico

This study reports length‐weight relationships and growth parameters for Floridichthys polyommus Hubbs, 1936 and Fundulus persimilis Miller, 1955 from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatan Peninsula, Mexico. Specimens were collected between April 2009 and March 2010. The resulting length‐weight relationship for F. polyommus was: W = 0.0180 Lt^3.37 and W = 0.0142 Lt^3.35 for F. persimilis. This study presents the first estimation for both species of the von Bertalanffy growth model parameters, the growth performance index, the L₅₀, and is the first report of the length‐weight relationship for F. persimilis.     

Reproductive traits of the “ocellated killifish” Floridichthys polyommus Hubbs, 1936 (Pisces: Cyprinodontidae) inhabiting estuary of the Champotón River (Campeche,Mexico)

This study explores the reproductive biology and the influence of environmental factors on the reproductive traits of Floridichthys polyommus inhabiting the estuary of the Champoton River. The analysis included population structure, gonadal developmental stages, reproductive period, size at first sexual maturity, fecundity, sex ratio, and somatic indexes. A spatio‐temporal pattern in the distribution of the seven size classes was detected. The species showed a positive allometric growth. Sex ratio was 1.21:1 (females:males). Size at first maturity was 42.23 mm (females) and 47.8 mm (males). A higher absolute and relative fecundity was detected in Puente Champotón estuary (PCH) with lower salinities than those detected in the Delta (DE). The adaptive significance of this trait could be in response to the heavy osmotic constraint imposed by extreme salinities in the DE. Floridichthys polyommus prefers PCH for spawning, and as a result a higher number of ripe individuals was observed in this site, characterized by the highest nutrient levels, which can boost productivity and food availability for fish. Hepatosomatic index was negatively correlated with gonadosomatic index, suggesting energy transfer from the liver towards gamete production. Floridichthys polyommus exhibits an opportunistic strategy (early maturity, small oocytes, small clutches) suggesting that energy is allocated towards reproduction to compensate for the unpredictable hydrological conditions imposed by the estuary (particularly during the hurricane season). Floridichthys polyommus shows a reproductive strategy exhibited by fish living in unstable systems. A seasonal divergence was observed in the reproductive traits of F. polyommus, while differences between study sites were for fecundity.     

Length‐weight relationship of fish species from the Bijagós Archipelago,Guinea‐Bissau

Length–weight relationships were estimated for six teleost fish species occurring in Bijagós Archipelago, Guinea‐Bissau. Samples were collected seasonally during three dry seasons (2013/2014, 2014/2015, 2015/2016) and two rainy seasons (2015 and 2016). Fishes were captured by three methods: angled from the beach or a boat; using beach seine with a mesh size ranging 0.5–1 cm; drift netting from a boat (mesh size 2 cm). This work provides the length‐weight relationship for three fish species that are not reported in FishBase (Citharichthys stampflii, Gerres nigri and Psettodes belcheri) as well as for three species from which we present a wider size range (Eucinostomus melanopterus, Scomberomorus tritor and Sphyraena afra).     

Length–weight relationships of six marine fish species from the coast of Ghana

This study estimated the LWRs of six fishes from the coastal waters of Greater Accra, Ghana. Data was obtained monthly from June 2018 to July 2019 and analyzed for total length and weight measurement to the nearest 0.1 cm and 0.01 g respectively. The sampling was done using hooks and line as well as monofilament and multifilament gear types. The mesh sizes for both monofilament and multifilament gear types ranged from 0.5 to 2 inches whereas the hooks types ranged from 6 to 12. The b values for the assessed species were within the range 2.8–3.2. There was strong correlation between the length and weight of all the species (R² > .95). This study provides LWRs for Cynoglossus senegalensis, Scorpaena histrio and Pseudotolithus senegalensis and larger maximum total length (TLmax) for Syacium micrurum, Eucinostomus melanopterus and Brachydeuterus auritus.     

Day and night trophic variations of dominant fish species in a lagoon influenced by freshwater seeps

The aim of this study was to determine the trophic structure and nycthemeral variations in the diet of dominant fish species (Ariopsis felis, Bairdiella chrysoura, Micropogonias undulatus, Eucinostomus gula, Eucinostomus argenteus, Lagodon rhomboides and Sphoeroides testudineus) in Celestun Lagoon, a biosphere reserve located in the southern Gulf of Mexico, and influenced by freshwater seeps. A total of 1473 stomachs were analysed and nine trophic groups were recorded. Bray–Curtis analyses with analyses of similarity (ANOSIM) statistical tests were used to determine two groups of feeding guilds: zoobenthivores and omnivores, with significant differences between time and habitat. The relationships between fish feeding habits, size class and environmental variables were investigated using canonical correspondence analysis (CCA). Most of the species showed a low niche breadth with high specialization towards amphipod consumption, with the exception of L. rhomboides (0·60), which indicated generalist feeding. This study in a protected area is an important source of information for drawing up conservation policies in relation to the management of aquatic resources, and will aid in the establishment of priority areas for conservation.     

Seasonal variations in the diversity,abundance, and composition of species in an estuarine fish community in the Tropical Eastern Pacific,Mexico

The ichthyofauna of the Chacahua Lagoon in the western Oaxaca State of Mexico was sampled every 2 months, using a trawl net over seven sampling cycles. The estuary mouth closed in late January, generating hypersaline conditions in the system. A total of 33 species belonging to 20 families were recorded; most of them marine species, showing tropical and subtropical affinities. The most abundant species were Diapterus peruvianus, Centropomus robalito, Anchovia macrolepidota, Lile stolifera, and Lutjanus novemfasciatus. Total fish abundance and species richness were not significantly affected by the mouth closing, and this was related to the presence of a permanently open entrance channel with an adjacent lagoon, which allowed easy exchange of fish between these two systems. Canonical correspondence analysis (CCA) revealed that salinity and dissolved oxygen were the most important environmental variables in determining the observed variability in fish community composition. Two fish groups were evident: the fish assemblage of the low-salinity period (open-mouth phase), in which Eucinostomus currani, Sciades guatemalensis, Centropomus armatus, Citharichthys stigmaeus, and Caranx caninus constituted the majority of the catch; and the fish assemblage of the high-salinity period (closed-mouth phase), with A. macrolepidota, L. stolifera, and Harengula thrissina as the most abundant species. Multivariate analyses showed differences in the composition of the fish community between both periods. Other species, such as the permanent residents D. peruvianus and C. robalito, which showed the widest range in tolerance of ambient salinity, were caught during both periods. Seasonal succession of fish populations may be related to differences in life cycle and tolerance of the environment among those species adapting to ecological conditions.     

Morphometric relationships for four Scombridae fish species in Australian waters

Morphometric relationships (length–weight and fork length–total length) were estimated for four scombrid species (Thunnus tonggol, Euthynnus affinis, Cybiosarda elegans, and Rastrelliger kanagurta) that are of growing importance to fisheries, but are also important predators representing different trophic levels in the neritic regime of Australian waters. The sample of 1,137 fish representing a broad size range for each species produced highly significant model fits (r² > .95) that provide researchers with reliable information for future biological studies, stock assessment, and ecosystem models.     

The weight‐length relationship of fish species found in the tidal creeks of the Amazon estuary,northern Brazil

The present study estimated the a and b parameters of the weight‐length relationship of five fish species that inhabit the tidal creeks of islands in the Amazon estuary: Colomesus asellus, Geophagus proximus, Lithodoras dorsalis, Pseudauchenipterus nodosus, Pachypops fourcroi. The species were collected quarterly between October 2013 to July 2014 using block nets made from 20 mm mesh size. The b coefficient of the regression of the weight on the total length of these species ranged from 2.71 to 3.14. These are the first reference on the weight‐length relationship for three species and the new maximum length recorded for two species.     

Conidial germination and germ tube elongation of Phomopsis amaranthicola and Microsphaeropsis amaranthi on leaf surfaces of seven Amaranthus species: Implications for biological control

Microsphaeropsis amaranthi and Phomopsis amaranthicola are potential biological control agents for several Amaranthus species. In an effort to understand the initial infection processes with these pathogens, a study was conducted of the conidial germination and germ tube length (μm) on the weed leaf surfaces at 21 °C and 28 °C. Weeds included Amaranthus rudis, A. palmeri, A. powellii, A. retroflexus, A. spinosus, A. hybridus, and A. albus. For P. amaranthicola, conidial germination and germ tube length varied among the seven weed species at both temperatures, while for M. amaranthi the differences in germ tube lengths were significant among weed species only at 21 °C. While the conidia of M. amaranthi and P. amaranthicola germinated on the leaf surfaces of all seven weed species, temperature appeared to impact the number and length of germ tubes on the leaf surfaces. The percentage of germinated conidia and the length of germ tubes at both temperatures were often greater for M. amaranthi than for P. amaranthicola. In order for the fungal pathogen to successfully infect and kill a weedy host, conidia must germinate and form a germ tube, two processes that vary with host species and temperature for M. amaranthi and P. amaranthicola. The extent to which successive infection processes, e.g., penetration, invasion and colonization, contribute to host specificity warrants study.     

Length‐weight and length‐length relationships of the genus Alosa (Clupeoidei: Clupeiformes: Clupeidae) along the southern Caspian Sea coast

Length–weight (LWR) and length–length (LLR) relationships were estimated for four shad species of the genus Alosa, reported from along the southern Caspian Sea coast, north of Iran in a study from March 2014. Two of these species are endemic to the Caspian Sea. The length–weight parameter b for these species ranged from 2.99 to 3.24, with regression coefficients (r²) ranging from 0.91 to 0.99. All LLRs were highly significant (r² > 0.96).     

Species diversity of the genus Osmundea (Ceramiales,Rhodophyta) in the Macaronesian region

Species diversity within the genus Osmundea in the Macaronesian region was explored by conducting a comprehensive sampling in the Azores, the Canary, and the Madeira archipelagos. Toward identification, all specimens were first observed alive to verify the absence of corps en cerise, a diagnostic character for the genus and morphometric data were measured (thallus length and width, first‐order branches length and width, branchlets length and width, cortical cell length and width in surface view, cortical cell length and width in transverse section). Specimens were sequenced for COI‐5P (39 specimens) and three species delimitation methods (Generalized Mixed Yule Coalescent, Automatic Barcode Gap Discovery method, and Poisson Tree Processes) were used to assess the threshold between infra‐ and interspecific relationships. Subsequently, one or several sequences of plastid‐encoded large subunit of RuBisCO (21 specimens) per delimited species were generated to assess the phylogenetic relationships among Macaronesian Osmundea. Moreover, for each delineated species, vegetative and reproductive anatomy was thoroughly documented and, when possible, specimens were either assigned to existing taxa or described as novel species. This integrative approach has provided data for (i) the presence of O. oederi, O. pinnatifida, and O. truncata in Macaronesia; (ii) the proposal of two novel species, O. prudhommevanreinei sp. nov. and O. silvae sp. nov.; and (iii) evidence of an additional species referred as “Osmundea sp.1,” which is a sister taxon of O. hybrida.     

The wing morphology of limnephilid caddisflies in relation to their habitat preferences

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Length–weight and length–length relationships for nine fish species from Lhasa River Basin,Tibet, China

The present study reports length–weight relationships (LWR) and length–length relationships (LLR) for five native freshwater fish species (Schizopygopsis younghusbandi, Triplophysa orientalis, T. tibetana, T. stewartii and T. stenura) and four introduced freshwater fish species (Pseudorasbora parva, Carassius auratus, Micropercops cinctus and Oryzias latipes) captured in the Lhasa River Basin, Tibet, China. Five of the LWRs are presented for the first time.     

Comparisons of morphology and esterase levels between Blattella germanica and Blattella nipponica (Blattodea: Blattellidae)

The habitat of the cockroach varies by species. The German cockroach, Blattella germanica, lives in human dwellings, while the Japanese field roach, Blattella nipponica, lives in a mountainous region. Based on phylogenetic analysis of mtCOI, the two species are closely related to each other and B. germanica is divergent from wild species such as B. nipponica. Their habitats and walking speed differ even though the two species have similar morphology. We hypothesized that habitats might influence walking speed by changes to appendage morphology and enzyme‐based physiological differences. We compared the length of the appendages and differences in a multifunctional enzyme superfamily, the esterases (EST, EC 3.1), including acetylcholinesterase (AChE, EC 3.1.1.7), which is related to central nervous system function. We found that phenotypes such as appendage length and esterase isozyme expression were clearly different between the two species. These differences might be responsible for the observed difference in walking speed.     

Utilization by fishes of shallow,seagrass-covered banks in Florida Bay: 2. Diel and tidal patterns

Synopsis Diel and tidal patterns in the occurrence of water column fishes were examined on four shallow banks in Florida Bay, using continuous 72h gillnet sets. Patterns in capture rates were presumed to indicate movement of fishes on and off the seagrass-covered banks. Species that were nocturnally active on the banks included Arius felis, Mugil gyrans, Opisthonema oglinum, Harengula jaguana, Elops saurus, Lutjanus griseus, and Bairdiella chrysoura. Diurnal species included Eucinostomus gula, Lagodon rhomboides and Mugil cephalus. Strongylura notata and Mugil curema showed no consistent patterns. At the two sites with significant tidal fluctuation in water level, different activity patterns on the bank relative to tidal stage were evident for several species. At extreme low tides, water column fishes apparently left the banks to avoid stranding. Cycles of fish utilization of the bank habitat are proposed to be related to both availability of prey (diel patterns) and water level (tidal patterns). These cycles in turn influence activity patterns of predators foraging on these fishes.     

Length–weight relationships of six species of the genera Cobitis and Sabanejewia (Cobitidae) in Iranian river systems

Length‐weight relationships (LWRs) were estimated for six spined loach species from Iran. Data were collected between 2010 and 2015. These represent the first reports of length–weight data for five of the species (Cobitis avicennae, Cobitis faridpaki, Cobitis keyvani, Sabanejewia aurata and Sabanejewia caspia) while also providing additional data on the remaining species (Cobitis linea). Five of these species are endemic and the remaining S. caspia, is native to the country. Estimated b values obtained for the studied species ranged from 2.381 for S. aurata to 3.411 for C. keyvani.     

Morphological and molecular differentiation of smooth‐hound sharks (Genus Mustelus,Family Triakidae) from the Gulf of California

The genus Mustelus is the most species‐rich of the widespread family Triakidae whereby its taxonomy and systematics have been historically challenging. They represent a significant fraction of the shark catches of small‐scale fisheries in the Gulf of California. In order to provide information useful for their management and conservation, the morphological and genetic distinction of the four species found in the northern Gulf of California (M. albipinnis, M. californicus, M. henlei and M. lunulatus) were analyzed. Discriminant analysis of 10 morphometric variables placed each species in a distinct and significantly different region of multivariate morpho‐space. The variables contributing most to their distinction were inter‐nostril width, mouth length, upper and lower labial furrow length, and mouth width. Restriction fragment length polymorphisms (PCR‐RFLP) of the nuclear ITS2 ribosomal DNA (rDNA) confirmed that each species represents a genetically cohesive and independent evolutionary lineage. In spite of the difficulty in differentiating these Mustelus species, a few cephalic measurements are useful to separate them. A PCR‐RFLP assay (using RsaI and MspI on ITS2 rDNA amplicons) is also proposed for the molecular differentiation of these commercially harvested smooth‐hound sharks, constituting the first molecular marker available for their identification. These data provide morphological and genetic tools that can be used to improve their management and conservation.     

Length–weight relationships of five endemic fish species from the lower Yarlung Zangbo River,Tibet, China

The length–weight relationships were estimated for five endemic fishes (Schizothorax curvilabiatus, Schizothorax molesworthi, Garra kempi, Neolissochilus hexagonolepis, Exostoma labiatum) from the Yarlung Zangbo River in Tibet, China. Fishing gear used for sampling included 4 cm mesh gill nets (100 m long × 1.2 m high) and electrofishing, from December 2015 to January 2016. Three of the species have new records of maximum length in FishBase.     

Length‐weight relationships of five Triplophysa species from the northwest of China

Length‐weight relationships were estimated for five Triplophysa species from the northwest China. A total of 1,598 specimens were collected using set gillnets (mesh size 1.5 cm) and ground bamboo cages in May 2012, and August 2014. This study presents the first references on LWRs for Triplophysa minuta, T. siluroides, and T. tenuis, and two new maximum length records for T. yarkandensis and T. strauchii. Statistical length–weight relationships for all five species were highly significant (p < .001), with R² values >.915.     

DNA barcoding of coastal ichthyofauna from Bahia,northeastern Brazil,South Atlantic: High efficiency for systematics and identification of cryptic diversity

In spite of the utility of DNA barcoding in discriminating marine fish species, few studies using this technique are available along the Brazilian coast, which encompasses nearly 9000 km, distinct biogeographic regions and endemism rates. Therefore, in the present work, we provided the first DNA barcode library based on sequencing of the mitochondrial gene cytochrome c oxidase subunit I (COI) for Actinopterygii fish from northeastern coast of Brazil. The database included 459 specimens from 54 genera, 31 families and 13 orders, with mean interspecific genetic distance of and mean intraspecific distance of 0.15%. As a result, the neighbor-joining (NJ) tree resulted in the molecular identification of 78 taxa. Cryptic species were indicated in Eucinostomus (mojarras) since the 82 specimens morphologically identified as Eucinostomus melanopterus or Eucinostomus sp. formed five clusters with intraspecific genetic distances up to 0.31% and lowest interspecific distance of 11.14%. Eucinostomus jonesii and Eucinostomus harengulus were identified for the first time in ichthyofauna inventories from northeastern Brazil. The present work has also added new records to the Barcode of Life Data System (BOLD), thereby favoring the identification of other specimens at different life stages or in forensic studies. The present dataset reinforces the reliability of DNA barcoding to estimate the overlooked richness of marine fish in Brazilian coast with application in conservation, ecology, systematics and fisheries.