Distribution of Japanese temperate bass, <Emphasis Type="Italic">Lateolabrax japonicus</Emphasis>, eggs and pelagic larvae in Ariake Bay

We collected eggs and larvae of the Japanese temperate bass, Lateolabrax japonicus, and present horizontal and temporal changes of distribution relative to development and growth during the species pelagic life history in Ariake Bay. Sampling was conducted from the inner to central region (11 sampling stations) of Ariake Bay using a plankton net (80 cm diameter, 0.5-mm mesh) from November 2000 to February 2001. Both eggs and larvae were collected most abundantly in mid-December. The CPUE of eggs in the surface layer was higher than the middle layer, which is in contrast to that at the larval stage. Most eggs were collected around the central and western regions of the bay. The distribution of eggs shifted vertically to the middle layer with development. Yolk-sac larvae were collected in the central region of the bay, and preflexion and flexion larvae were more abundantly collected in the inner region of the bay. The body length of larvae around the inner bay was larger than in the central region. The pelagic life history can be summarized as follows: eggs are distributed around the central region of the bay and eggs and larvae expand their distribution to the inner and shallower waters with growth. We conclude that the shift of vertical distribution in pelagic stages and the hydrographic features of the middle layer form one of the mechanisms enabling the inshore migration of L. japonicus.     

Life history of peracarid species in South‐western Atlantic: Comparison of population traits between native and exotic species

Life‐history traits of exotic species are important to understand the process involved in their settlement and their potential impact on native biodiversity. In this context, the seasonal density, the population structure and the reproductive patterns of exotic and native peracarid species of two natural marine environments of Southwestern Atlantic were studied in order to determine the traits that favour the invasion success of exotic species. Five samples, consisted of algal patches (0.20 × 0.20 m quadrants), were collected seasonally from 2016 to 2017 in two intertidal environments (La Estafeta and Cerro Avanzado). Both environments presented high richness of cryptogenic and exotic species (Tanais dulongii, Monocorophium insidiosum, Ampithoe valida, Melita palmata and Jassa marmorata), and only two native species were recorded (Apohyale grandicornis and Exosphaeroma lanceolatum). The comparison of life‐history traits suggested that the distribution, dominance and the highest densities of some exotic species are closely related to their continuous reproductive and recruitment periods, their capability to adapt their life‐history strategies to different environmental conditions and to a more efficient distribution of resources during reproduction; however, in native species, only A. grandicornis registered similar life‐history traits than exotic populations, suggesting that their distribution could be limited by a latitudinal gradient. We expect that these results provide essential information to understand the invasion pattern of exotic species and their potential impact on native biodiversity in Southwestern Atlantic.     

Low interbasin connectivity in a facultatively diadromous fish: evidence from genetics and otolith chemistry

Southern smelts (Retropinna spp.) in coastal rivers of Australia are facultatively diadromous, with populations potentially containing individuals with diadromous or wholly freshwater life histories. The presence of diadromous individuals is expected to reduce genetic structuring between river basins due to larval dispersal via the sea. We use otolith chemistry to distinguish between diadromous and nondiadromous life histories and population genetics to examine interbasin connectivity resulting from diadromy. Otolith strontium isotope (⁸⁷Sr:⁸⁶Sr) transects identified three main life history patterns: amphidromy, freshwater residency and estuarine/marine residency. Despite the potential for interbasin connectivity via larval mixing in the marine environment, we found unprecedented levels of genetic structure for an amphidromous species. Strong hierarchical structure along putative taxonomic boundaries was detected, along with highly structured populations within groups using microsatellites (F_ST = 0.046–0.181), and mtDNA (Φ_ST = 0.498–0.816). The presence of strong genetic subdivision, despite the fact that many individuals reside in saline water during their early life history, appears incongruous. However, analysis of multielemental signatures in the otolith cores of diadromous fish revealed strong discrimination between river basins, suggesting that diadromous fish spend their early lives within chemically distinct estuaries rather than the more homogenous marine environment, thus avoiding dispersal and maintaining genetic structure.     

Age‐based demographics of the pearl perch Glaucosoma scapulare (Ramsay, 1881)

This research represents the first age‐based demographic assessment of pearl perch, Glaucosoma scapulare (Ramsay, 1881), a highly valued species endemic to coastal waters off central eastern Australia. The study was conducted across the species' distribution that encompasses two state jurisdictions (Queensland in the north and New South Wales in the south) using data collected approximately 10 years apart in each state. Estimates of age were made by counting annuli (validated using marginal increment ratios) in sectioned sagittal otoliths. The maximum estimated age was 19 years. Pearl perch attained approx. 12 cm fork length (FL) after one year, 21 cm FL after 2 years and 29 cm FL after 3 years. Fish from the southern end of the species' distribution grew significantly more slowly than those from the northern part of its range. Commercial landings in the north were characterized by greater proportions of larger (>40 cm FL) and older (>6 years) fish than those in the south, with landings mainly of fish between 3 and 6 years of age. The observed variations in age‐based demographics of pearl perch highlight the need for a better understanding of patterns of movement and reproduction in developing a model of population dynamics and life‐history for this important species. There is a clear need for further, concurrent, age‐based studies on pearl perch in the northern and southern parts of its distribution to support the conclusions of the present study based on data collected a decade apart.     

Length‐weight relationship of three cichlid species in a stream in southwestern Amazon,Brazil

The paper investigates the length‐weight relationship of three cichlids species for the southwestern Amazon, Acre state. The individuals were collected at five sites during one year among august/2016 and june/2017 in Quinoá stream (10°06′03.33″S/67°40′11.50″W). The individuals were collected using: seine net, 6 m length, 2.25 high, and mesh size 5 mm, two dip nets, 5 mm mesh, 30 cm width, and 50 cm in length and two sieve with 5 mm mesh, 50 cm width, and 80 cm in length. The results show that one species presented positive allometric growth (Aequidens tetramerus) and the others negative allometric growth (Apistogramma acrensis and Crenicichla semicincta).     

Age,growth and reproductive traits of invasive goby Taenioides cirratus in the Chaohu Lake,China

The eel goby Taenioides cirratus (Blyth, 1,860) is a small fish inhabits muddy bottoms of brackish-water in the Indo-West Pacific. It has invaded many inland freshwater lakes in China, such as the Chaohu Lake, Gaoyou Lake and Nansi Lake, and its population increased rapidly in these freshwater lakes in recent years. The age, growth and reproductive traits of T. cirratus invading the Chaohu Lake were studied. A total of 482 specimens (210 females, 204 males and 68 juveniles) with total length (TL) ranging from 9.4 to 20.6 cm were collected using the benthic fyke nets at monthly intervals from March 2018 to February 2019. The sagittal otolith was used for age determination. Monthly variation of marginal increment ratio indicated that the annual forming of opaque band on sagittal otolith was completed during March and April. For both sexes, only four (from 0+ to 3+ years) age groups were observed and 1+ and 2+ years age individuals dominated the population. Back calculated length at age showed males grew faster than females. Both sexes reached maturity at 1+ year age and the TL at first maturity (TL₅₀) was 12.6 cm for females and 11.9 cm for males. Monthly variation of gonado-somatic index indicated that the spawning occurred from May to August. The fecundity ranged from 967 ova to 5,114 ova, with a mean of 3,205 ova. Our study provides a comprehensive data on the key life history traits of T. cirratus for the first time.     

Rainforest fragmentation and the demography of the economically important palm <Emphasis Type="Italic">Oenocarpus bacaba</Emphasis> in central Amazonia

We summarize a long-term study of the effects of edge creation on establishment of the economically important arboreal palm Oenocarpus bacaba in an experimentally fragmented landscape in central Amazonia. Recruitment and mortality of large individuals (≥10 cm diameter-at-breast-height) were recorded within 21 1-ha plots in fragmented and intact forests for periods of up to 22 years. In addition, 12 small (0.7 × 14 m) sub-plots within each 1-ha plot were used to enumerate the abundance of seedlings and saplings (5–400 cm tall). On average, the recruitment of large trees was over two times faster near forest edges, leading to a sharp (90%) increase in the mean population density of large individuals near forest edges, whereas the density of larger trees remained constant in the forest interior. Overall seedling and sapling density was significantly lower in edge than interior plots, but edge plots had a much higher proportion of larger (>100 cm tall) saplings. Our findings demonstrate that forest edges can have complex effects on tree demography and that one must consider all tree life stages in order to effectively assess their effects on plant populations.     

Length–weight relationships of four marine fish species caught in the South China Sea

Length–weight relationships are described for four marine teleost fish species caught in the South China Sea. A total of 625 individuals were collected from April to August 2007 and November 2012 using a bottom trawl (mesh size, 3.9 cm) and longline fishing. The values of parameters a and b ranged from 0.004612 to 0.02137 and 3.019 to 3.371, respectively. The high r² values (all >.950) indicate that these relationships are robust and will be appropriate for use in fisheries management of these species.     

Length–weight and length–length relationship of two endemic snakehead fish species from Brahmaputra river basin,Assam, India

Length–weight relationships (LWRs) and length–length relationships (LLRs) of two endemic Channid fish species, Channa aurantimaculata Musikasinthorn, 2000 and C. stewartii (Playfair, 1867) were studied from Brahmaputra River basin in Assam, India. Sampling was done from May to December, 2017 and a total of 81 fish specimens were collected using bamboo traps. In the LWRs, b value for C. aurantimaculata and C. stewartii were 3.0456 and 2.9172 respectively. Maximum size recorded for C. aurantimaculata in the present study (34.1 cm) was higher than previous record in FishBase (19.1 cm).     

Spatial and temporal changes in the fish communities from a mangrove‐dominated creek system near Karachi,Pakistan

The objectives of the study were to inventory the fish community, examine how the fish communities changed in these creeks temporally (season), and compare the fish communities between creeks of varying structure (width). During February 1999 to December 2001, a survey was undertaken to monitor the distribution and abundance of fishes in the Korangi‐Phitti Creek (KPC) system (24°45′N, 67°20′E) near Karachi, Pakistan. Fish were collected from 123 stations using a combination of monofilament gillnets of 8.9 cm, 5.7 cm, and 3.8 cm stretched mesh sizes. A total of 17 023 fish representing 86 species were collected during the study; Sardinella gibbosa and Nematalosa nasus were the most abundant taxa (in terms of numbers of individuals) collected, accounting for over 60% of the total catch. Physical conditions in the study area were found to have significant seasonal (monsoon) patterns related more to temperature and salinity than to rainfall. Seasonal comparisons indicated that the communities were significantly different between the northeast monsoon (NEM) and southwest monsoon (SWM) seasons. Taxa primarily responsible for distinguishing the NEM were the mullets (Moolgarda cunnesius, Liza carinata, Mugil cephalus). The SWM was characterized by Anodontostoma chacunda, Scomberoides commersonnianus, and the engraulid (Thryssa hamiltonii). The community sampled in wide creeks (shipping channels) was very different in composition than the community in small creeks within this system. Wide creeks were characterized by schooling pelagic species (S. gibbosa, N. nasus), while the smaller creeks were characterized by the presence of mullets (M. cunnesius, M. cephalus, L. carinata) and scat (Scatophagus argus). The KPC system was shown to contain a highly diverse fishery, which in turn contributes to regional offshore fisheries (shad, mackerel, tuna and perches). The various negative natural and anthropogenic events in this region highlight the need for information regarding the fish community, water quality, and the mangrove forest to evaluate ecosystem changes, the effects of disturbances, and for the development and making of sound management decisions.     

Age,growth, maturity and mortality of the tapetail anchovy Coilia brachygnathus (Engraulidae) in Lake Honghu,China

The tapertail anchovy Coilia brachygnathus, a commercially important species mainly distributed along the mid-lower Chang-Jiang basin, is by far the most dominant species in Lake Honghu. To figure out its success in this semiclosed lake, some basic biological parameters of this anchovy were analysed based on samples seasonally collected from October 2020 to December 2021. The results demonstrated that the age classes of fished individuals varied from 0.5 to 3.5, with the majority (97.36%) being between 0.5 and 3 years old. The size at 50% maturity of 17.2 cm total length (TL) for females and 19.0 cm TL for males corresponded to 1 and 1.6 years, respectively. Coilia brachygnathus has a short life span, early sexual maturity and a relatively fast growth rate. The flourishing of the fish in the lake is mainly attributed to its short life span, early maturity, fast growth rate, closed fishing, pelagic spawners, the availability of plenty of food and low predation effect on it. Age 3.5 year occurs in an extremely small percentage of the total (<3%), indicating that a large number of larger-sized or older fish died after spawning, which is probably one of the major sources of water pollution if the closed fishing measure is adopted in Lake Honghu. Thus, individuals older than 2 years or more than 20.0 cm TL should be harvested. These findings have important management implications for the fish resources in Lake Honghu and beyond.     

Using cross-dating techniques to validate ages of aurora rockfish (<Emphasis Type="Italic">Sebastes aurora</Emphasis>): estimates of age,growth and female maturity

Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish (Sebastes aurora) may have increased. Understanding the life history of these species is a critical first step in developing management strategies to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises, over the years 2003–2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The maximum estimated age was 118 years for females (n = 324) and 81 years for males (n = 114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males: L _inf = 34, K = 0.09, t ₀ = −1.9; females: L _inf = 37, K = 0.06, t ₀ = −5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were calculated at 12.6 years and 26 cm, respectively (n = 307). Maturity and age data provided evidence for a protracted adolescence in this species.     

Extreme plasticity in life‐history strategy allows a migratory predator (jumbo squid) to cope with a changing climate

Dosidicus gigas (jumbo or Humboldt squid) is a semelparous, major predator of the eastern Pacific that is ecologically and commercially important. In the Gulf of California, these animals mature at large size (>55 cm mantle length) in 1–1.5 years and have supported a major commercial fishery in the Guaymas Basin during the last 20 years. An El Niño event in 2009–2010, was accompanied by a collapse of this fishery, and squid in the region showed major changes in the distribution and life‐history strategy. Large squid abandoned seasonal coastal‐shelf habitats in 2010 and instead were found in the Salsipuedes Basin to the north, an area buffered from the effects of El Niño by tidal upwelling and a well‐mixed water column. The commercial fishery also relocated to this region. Although large squid were not found in the Guaymas Basin from 2010 to 2012, small squid were abundant and matured at an unusually small mantle‐length (<30 cm) and young age (approximately 6 months). Juvenile squid thus appeared to respond to El Niño with an alternative life‐history trajectory in which gigantism and high fecundity in normally productive coastal‐shelf habitats were traded for accelerated reproduction at small size in an offshore environment. Both small and large mature squid, were present in the Salsipuedes Basin during 2011, indicating that both life‐ history strategies can coexist. Hydro‐acoustic data, reveal that squid biomass in this study area nearly doubled between 2010 and 2011, primarily due to a large increase in small squid that were not susceptible to the fishery. Such a climate‐driven switch in size‐at‐maturity may allow D. gigas to rapidly adapt to and cope with El Niño. This ability is likely to be an important factor in conjunction with longerterm climate‐change and the potential ecological impacts of this invasive predator on marine ecosystems.     

Re‐examining extreme longevity of the cave crayfish Orconectes australis using new mark–recapture data: a lesson on the limitations of iterative size‐at‐age models

1. Centenarian species, defined as those taxa with life spans that frequently exceed 100 years, have long been of interest to ecologists because they represent an extreme end point in a continuum of life history strategies. One frequently reported example of a freshwater centenarian is the obligate cave crayfish Orconectes australis, with a maximum longevity reported to exceed 176 years. As a consequence of its reported longevity, O. australis has been used as a textbook example of life history adaptation to the organic‐carbon limitation that characterises many cave‐stream food webs. 2. Despite being widely reported, uncertainties surround the original estimates of longevity for O. australis, which were based on a single study dating from the mid‐1970s. In the present study, we re‐evaluated the growth rate, time‐to‐maturity, female age‐at‐first‐reproduction and longevity of O. australis using a mark–recapture study of more than 5 years based upon more than 3800 free‐ranging individuals from three isolated cave streams in the south‐eastern United States. 3. The results of our study indicate that accurate estimates of the longevity of O. australis are ≤22 years, with only a small proportion of individuals (<5%) exceeding this age. Our estimates for female time‐to‐maturity (4–5 years) and age‐at‐first‐reproduction (5–6 years) are also substantially lower than earlier estimates. 4. These new data indicate that the age thresholds for life history events of O. australis are comparable to other estimates for a modest assemblage of cave and surface species of crayfish for which credible age estimate exists, suggesting that a cave environment per se is not required for the evolution of extreme longevity in crayfish.     

Life history variation among years in a brackish water type of the Ninespine Stickleback, <Emphasis Type="Italic">Pungitius pungitius</Emphasis>

The life history variation in a brackish water type of the Ninespine Stickleback Pungitius pungitius collected over 3 years was studied by examining the strontium (Sr) and calcium (Ca) concentrations in the otoliths. The life histories showed the fish were either brackish water residents or anadromous throughout those years. 74–78% of the fish had the former life history and 22–26% the latter. The composition of each life history was constant throughout the 3 years, and the occurrence of the “anadromous” novel life history found previously is a general phenomenon in this species.     

Complex spatial structure in a population of <Emphasis Type="Italic">Didymopanax pittieri</Emphasis>, a tree of wind-exposed lower montane rain forest

Didymopanax pittieri is a common shade-intolerant tree colonizing treefall gaps in the elfin forests on windswept ridgecrests in the lower montane rain forests of the Cordillera de Tilarán, Costa Rica. All D. pittieri taller than >0.5 m in a 5.2-ha elfin forested portion of a gridded study watershed in the Monteverde Cloud Forest Preserve were located, mapped, and measured. This local population of D. pittieri is spatially inhomogeneous, in that density increases with increasing wind exposure; D. pittieri are more abundant near ridge crests than lower on windward slopes. The important and ubiquitous phenomenon of spatial inhomogeneity in population density is addressed and corrected for in spatial analyses by the application of the inhomogeneous version of Ripley’s K. The spatial patterns of four size classes of D. pittieri (<5 cm dbh, 5–10 cm dbh, 10–20 cm dbh, and >20 cm dbh) were investigated. Within the large-scale trend in density driven by wind exposure, D. pittieri saplings are clumped at the scale of treefall gaps and at the scale of patches of aggregated gaps. D. pittieri 5–10 cm dbh are randomly distributed, apparently due to competitive thinning of sapling clumps during the early stages of gap-phase regeneration. D. pittieri larger than 10 cm dbh are overdispersed at a scale larger than that of patches of gaps. Natural disturbance can influence the distribution of shade intolerant tree populations at several different spatial scales, and can have discordant effects at different life history stages.     

Reproductive biology of Bigeye Tuna, <Emphasis Type="Italic">Thunnus obesus</Emphasis>, (Scombridae) in the eastern and central tropical Pacific Ocean

Understanding the reproductive potential of any species is of great importance for resource assessment and management. We studied the reproductive biology of Bigeye Tuna, Thunnus obesus, based on 1283 samples taken from the Chinese longline vessels in the eastern and central Tropical Pacific Ocean during February through November 2006. The female-male ratio was 1.0 : 1.5 and males were predominant in all length classes except for the length class of 166–170 cm (fork length). Males dominated in sizes larger than 171 cm, all specimens of 192 cm or larger were males. The main spawning period of Bigeye Tuna was between March and November. Gonadosomatic rates of males were larger than those of females. Statistically, female and male Bigeye Tuna had no significant reproductive seasonality. The observed minimum length at sexual maturity for female Bigeye Tuna was 94 cm. Length at 50% sexual maturity of female Bigeye Tuna was estimated at 107.8 cm, and maturation rate was 0.106 cm⁻¹. The results derived in this study provide the information critical to our understanding of key life history parameters of Bigeye Tuna in tropic Pacific Ocean.     

Contrasting demographic history and gene flow patterns of two mangrove species on either side of the Central American Isthmus

Comparative phylogeography offers a unique opportunity to understand the interplay between past environmental events and life‐history traits on diversification of unrelated but co‐distributed species. Here, we examined the effects of the quaternary climate fluctuations and palaeomarine currents and present‐day marine currents on the extant patterns of genetic diversity in the two most conspicuous mangrove species of the Neotropics. The black (Avicennia germinans, Avicenniaceae) and the red (Rhizophora mangle, Rhizophoraceae) mangroves have similar geographic ranges but are very distantly related and show striking differences on their life‐history traits. We sampled 18 Atlantic and 26 Pacific locations for A. germinans (N = 292) and R. mangle (N = 422). We performed coalescence simulations using microsatellite diversity to test for evidence of population change associated with quaternary climate fluctuations. In addition, we examined whether patterns of genetic variation were consistent with the directions of major marine (historical and present day) currents in the region. Our demographic analysis was grounded within a phylogeographic framework provided by the sequence analysis of two chloroplasts and one flanking microsatellite region in a subsample of individuals. The two mangrove species shared similar biogeographic histories including: (1) strong genetic breaks between Atlantic and Pacific ocean basins associated with the final closure of the Central American Isthmus (CAI), (2) evidence for simultaneous population declines between the mid‐Pleistocene and early Holocene, (3) asymmetric historical migration with higher gene flow from the Atlantic to the Pacific oceans following the direction of the palaeomarine current, and (4) contemporary gene flow between West Africa and South America following the major Atlantic Ocean currents. Despite the remarkable differences in life‐history traits of mangrove species, which should have had a strong influence on seed dispersal capability and, thus, population connectivity, we found that vicariant events, climate fluctuations and marine currents have shaped the distribution of genetic diversity in strikingly similar ways.     

Analysis of genetic structure of the red shrimp <Emphasis Type="Italic">Aristeus antennatus</Emphasis> from the Western Mediterranean employing two mitochondrial regions

In this paper we addressed the phylogeographical genetic structure of the economically important red shrimp, Aristeus antennatus (Crustacea, Aristeidae) in the Western Mediterranean. Partial mitochondrial regions of the cytochrome c oxidase subunit I (514 bp) and ribosomal 16S subunit (547 bp) were sequenced in 137 individuals collected at three localities: Catalan Sea, Ligurian Sea and the southern Tyrrhenian Sea. Values of haplotypic diversity were h = 0.552–0.724, whereas those for nucleotide diversity were π = 0.0012–0.0026. Among-sample genetic diversity was not significant and no geographical patterns in the distribution of haplotypes were apparent. Results of the present study are consistent with a past population expansion that occurred <2,000 years ago. Despite the current fishing pressure, genetic variability appears to be sufficiently high to keep A. antennatus populations stable over time. Dispersal-related life history traits may account for the shallow genetic structure. Our results are not in contrast with the hypothesis of sustainability of Western Mediterranean red shrimp fisheries predicted on the basis of previously obtained biological results.     

Length weight relationships of five marine fishes from the Bay of Bengal

Length weight relationships (LWR) of five marine fishes were estimated from the Bay of Bengal, Bangladesh. Fish samples were collected occasionally from fisher's catch with gill net (mesh size: 3 cm) during November 2019 to October 2020. Fishing was done overnight. Total length (0.1 cm) and body weight (0.01 g) of each individual were measured. We recorded maximum total length for P. maculatus (55.0 cm) and P. parmatus (39.0 cm).