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Climate change threatens fisheries health through changing ecosystem dynamics; however, the impacts on the physiology and ecology of commercial fish populations are unclear. Here, annually deposited growth increments of female yelloweye rockfish (Sebastes ruberrimus) opercula collected in the Gulf of Alaska were used to successfully reconstruct lifetime (∼1-year resolution) steroid hormone, stable isotope, spawning, and stress data. We assessed how hormone profiles, spawning and distress frequencies related to sea surface temperature (SST), chlorophyll a concentrations as well as climate indices. Further, we assessed whether incorporating indicators of foraging depth and diet, stable isotope values (ẟ13C and ẟ15N), would improve model interpretations. Progesterone and estradiol concentrations decreased with increasing SST, suggesting that increasing SSTs may negatively impact juvenile and subadult females' reproductive development. Spawning frequency was positively linked to changes in the North Pacific Gyre Oscillation (NPGO) index, potentially timed with favorable conditions for larval survival. This was supported by juveniles having a lower probability of a distress event during positive NPGO years compared to negative NPGO years. While relationships among environmental data and yelloweye rockfish physiology were weak, this study provides insight into the environmental impacts on the lifetime reproduction and stress of a commercially important teleost species. [ABSTRACT FROM AUTHOR]

Investigations on sexual reproduction of jellyfish are essential to understanding mechanisms and patterns of outbreaks formation. Pelagia noctiluca (Forskål, 1775) (Scyphozoa) is known as the predominant jellyfish species with direct development in Western and Central Mediterranean Sea. In this paper we used integrated morphometric, histological, and biochemical approaches to investigate the annual reproductive biology of P. noctiluca from the Strait of Messina (South Thyrrenian Sea), a key proliferation area for this species due to favourable temperatures and high productivity. From November 2011 to September 2012, P. noctiluca sexual reproduction occurred throughout the year, with two seasonal peaks (autumn, spring) of spawning and embryonic development. Gonads of female P. noctiluca were characterized by a large amount of mature eggs of small size (diameter < 200 μm) during high food availability, whereas fewer, larger eggs (diameter > 200 μm) were detected during low availability of prey. Two morphometric indexes were applied: the Gonad-Somatic Index (GSI, gonadal/somatic tissue dry weight ratio) and Fecundity Index (FI, n° eggs mm −2 * gonadal dry weight). The FI showed longer spawning periods than the GSI, providing a better causal-mechanistic explanation for the year-round occurrence of P. noctiluca in the Strait of Messina. Protein contents of the gonads changed seasonally, with the highest concentrations during the pre-spawning periods. We suggest that investigations on jellyfish sexual reproduction can provide biological information relevant for understanding mechanisms of jellyfish blooms as well as for the management of coastal zones affected by outbreaks of gelatinous species. [ABSTRACT FROM AUTHOR]

Ruditapes philippinarum, a venerid clam, is a dominant species in the sandy and muddy areas in the coastal waters of the Marmara Sea. Intensive commercial harvesting of this species is conducted in these regions. We studied the population dynamics of R. philippinarum on the southern coast of the Marmara Sea (Bandırma). Samples were collected on a monthly basis between September 2012 and August 2013. Seasonal von Bertalanffy growth parameters using the length-frequency distribution of R. philippinarum were estimated at L = 67.50 mm and K = 0.33 year, and the seasonal oscillation in growth rate was 0.53. The slowest growth period was in January. The growth performance index and potential lifespan were 3.182 and 8.06 years, respectively. The growth relationship was confirmed to have a positive allometric pattern. The average total mortality rate was estimated to be 0.777 year, whereas the natural and fishing mortality rates were 0.539 and 0.238 year, respectively. The current exploitation rate of R. philippinarum was 0.306. The recruitment pattern peaked during June-August, and spawning occurred between May and August. The results of this study provide valuable information on the status of R. philippinarum stocks. [ABSTRACT FROM AUTHOR]

This study indicated that the life-history traits of European barracuda Sphyraena sphyraena are apparently better suited to their environmental conditions compared to the more physically restricted life-history traits of the yellow-mouth barracuda Sphyraena viridensis, which co-habit the north-western Mediterranean Sea. The latter thermophilic species has a considerably higher reproductive potential as it invests its energy reserves in larger numbers of hydrated eggs per spawning batch. This would favour its population growth rates within the study area, especially if sea warming continues, in which case it is likely that the spawning phenology of this species would give it an advantage. [ABSTRACT FROM AUTHOR]

Key biological characteristics of the harlequin fish Othos dentex, a representative of a monospecific genus of the Anthiinae (Serranidae), were determined from samples collected around reefs on the south coast of Western Australia. The females of this relatively long-lived species (maximum recorded age in this study = 37 years) attained only a slightly greater maximum total length and age than males and neither the length nor the age-frequency distributions showed a conspicuous sex-based bimodality. Furthermore, gonads from a wide size and age range of O. dentex were shown by histology, at several locations along their length, to always comprise exclusively either ovarian or testicular tissues. Thus, O. dentex is a gonochorist, a sexual pattern only previously recorded definitively for one other anthiine serranid, i.e. Epinephelides armatus, which also occurs in south-western Australia. Similar to E. armatus, O. dentex possesses 'solid' testes with a central sperm duct, thereby differing in structure from those typically found in serranids, in which there is a central membrane-bound 'ovarian' lumen and peripherally located sperm sinuses. The gonadal characteristics and sexual pattern of these two gonochoristic anthiines are not consistent with a recent proposal for the trends exhibited by the evolution of gonochorism and protogyny within the Serranidae. Othos dentex has indeterminate fecundity and a protracted spawning period (7 months) and, on the basis of underwater observations and a low gonado-somatic index ( IG) for males, is a pair spawner, which is unusual for a gonochorist of a serranid or member of a related family. While the large spots on the lower half of the body of O. dentex are shown quantitatively to be similarly yellow in juveniles and adult females, they then become blue in males at maturity and this intensifies during the spawning period, when they presumably play an important role in agonistic interactions among males and courtship with females. The attainment of maturity and rapid growth by O. dentex early in life may reflect selection pressures to reduce predation mortality during that period. Total mortality in the population is moderately low during later life, implying that the current fishing pressure on O. dentex is relatively light. [ABSTRACT FROM AUTHOR]

Fluctuations in the number and size of spawning perch ( Perca fluviatilis) in Lake Geneva were evaluated and compared each year from 1984 to 2011 in two locations. This evaluation was based on: (1) each mature female lays only one egg strand per year and (2) the number and size of mature females are well correlated with those of their egg strands. Egg strands were counted and measured at two locations in France and in Switzerland. The collection of egg strands from either artificial substrates (France) or by direct sampling of the natural lake bottom by a diver (Switzerland) did not seem to affect the results. In most years the number and mean width of egg strands fluctuated in the same way in both locations. In addition, yearly perch catches were correlated with the number of egg strands at both locations. However, more small egg strands were found in France than in Switzerland, whereas the reverse was true of large egg strands. Fishing pressure concentrated to a greater extent on small perch in France than in Switzerland could explain this difference. [ABSTRACT FROM AUTHOR]

This study investigated demographic structure and reproductive characteristics of the Atlantic mackerel Scomber scombrus, in relation to landing trends in the northern-central Adriatic Sea. Results highlighted the occurrence of only small-sized and young-age individuals, and a marked decline from the 1990s to the present in maximum age (from 8 to 3 years) and total length ( LT; from 420 to 360 mm). Fecundity ranged between 40 000 and 190 000 eggs, and was related to female LT. High levels of atresia implied lower values of actual fecundity. Sexual maturity was attained by 72·8% of individuals in their first year of life at 200 mm. The reduction in maximum LT resulted in a marked decline in the population egg production, while the reduction in maximum age implied that females participated in fewer spawning events. [ABSTRACT FROM AUTHOR]

Abstract: Female winter flounder were examined using gonad histology to determine the adequacy of routine macroscopic maturity classification methods and to determine the spatial variation in size and age of maturity in U.S. waters. Sampling occurred in spring and autumn, which was adequate to collect immature, mature, spawning-active, and non-active females. Females were collected in coastal waters from Delaware Bay, USA, to the Scotian Shelf, Canada, including in Long Island Sound and on Georges Bank, which covered all U.S. stock areas. Mature fish spawned in spring, when gonads comprised up to 30% of the total body weight. Direct comparisons of maturity assignment by macroscopic versus microscopic methods demonstrated that both schemes are compatible, but the more cost-effective macroscopic method had trouble distinguishing larger immature from smaller resting females. Spatial comparisons, using gonad histology only, supported the existence of three stocks in U.S. waters, but also revealed significant variation in age at maturity within the two coastal stocks. Age-at-maturity was more variable than size-at-maturity, which is consistent with known stock-specific patterns of growth rates and a postulated life history tradeoff to delay maturity until a size threshold is reached. The within-stock variation in median age at maturity, about one year for coastal stocks, recommends further investigation of using static, stock-specific maturity ogives to calculate reference points for management. [Copyright &y& Elsevier]

Abstract: The age, growth and reproductive biology of bluemouth, Helicolenus dactylopterus were studied in order to assess the use of these life history parameters as possible population discriminators in Portuguese waters. Fish were obtained from commercial landings in mainland Portugal (Peniche), Azores, and Madeira and supplementary samples were obtained from research surveys in the Portuguese continental slope. Significant differences in mean total-length and mean length-at-age were found between the three areas. The reproductive biology was analysed using the annual sexual cycle, three bionergetic indexes and the maturity ogives. Individuals presented a similar reproductive strategy in Portuguese waters with asynchrony of sexual cycles, similar female spawning season in the three areas and a sperm retention period in the ovaries of 1 to 6–7 months. The bionergetic indexes showed significant differences through the maturative stages and among areas. No significant differences were obtained when comparing the length at first maturity between mainland Portugal and Azores for both sexes. The results of this study will provide a comprehensive understanding of this species life history and presented useful evidence that can support the presence of different populations in the Portuguese waters. [Copyright &y& Elsevier]

The associations were quantified between daily and interannual variation in the timing of a closed population of lake sturgeon Acipenser fulvescens migration and arrival at spawning sites with stream environmental and lunar covariates. Spawning data were gathered from 1262 fish in Black Lake, Michigan 2001 to 2008 and by video monitoring 2000 to 2002. Sex-specific variation in responses to external cues was also tested. Results showed that a greater number of individuals initiated migration from lake to riverine habitats at dawn and dusk relative to other times of the day. Current and lagged effects of water temperature and river discharge, and periods in the lunar cycle were important variables in models quantifying movements into the river and timing of adult arrival at spawning sites. Different suites of covariates were predictive of A. fulverscens responses during different periods of the spawning season. The timing of initiation of migration and spawning, and the importance of covariates to the timing of these events, did not differ between sexes. Stream flow and temperature covaried with other variables including day length and the lunar cycle. Anthropogenic disruption of relationships among variables may mean that environmental cues may no longer reliably convey information for Acipenseriformes and other migratory fishes. [ABSTRACT FROM AUTHOR]

Abstract: White hake (Urophycis tenuis) provides an important fishery in the Gulf of Maine (GOM) that is currently depleted. Even though several year classes are present, there is little evidence of white hake reproduction occurring along the northern coastal shelf. Based on survey indices of early life history stages, researchers concluded that they reproduced at one of the two population centers located either from the Scotian Shelf area in eastern GOM or from the Georges Bank-Mid Atlantic Bight area. White hake have been absent from large areas of the GOM for more than 15 years and this suggests substantive changes may have occurred in their distribution since the 1920s. Various factors may have contributed to this observation, including the loss of spawning aggregations. This study examined the historical population structure of white hake in the Gulf during the 1920s, a period when stocks were more abundant. Their seasonal distribution, movement patterns and the behavior of individual population components were derived from relevant scientific literature and surveys of fishermen gathered during the period. The study identified several resident groups of white hake near the coastal shelf that displayed cyclic movement patterns to fishing grounds that have been abandoned for decades. The comparison of historical distribution patterns to recent white hake surveys revealed the loss of resident white hake groups from grounds bordering the northern GOM coastal shelf that apparently were undetected spawning components. Significance of the predator–prey linkage with alewives is discussed. [Copyright &y& Elsevier]

- The River Purtse was historically a significant Atlantic salmon spawning river in the Gulf of Finland (Baltic Sea). After the establishment of oil shale mining and processing in the catchment area in the late 1920s, the salmon population went extinct. By the 1970s, the river was heavily polluted and the lower reaches lacked any fish fauna. However, since the 1990s, pollution from oil shale mines was greatly reduced and water quality started to improve. The first fish species to repopulate the polluted area were gudgeon and nine-spined stickleback. The first salmon parr from wild spawning were recorded in 2006. Up to 2009, a total of fifteen fish species have been recorded including trout and the sensitive bullhead. This study illustrates the natural recovery of the fish fauna following water quality improvement. [ABSTRACT FROM AUTHOR]

Population mean egg size of salmonids increases with the mean size of gravels in which a population spawns. A long-standing hypothesis is that large larvae cannot navigate small-gravel interstices, so mothers must decrease per-offspring investment when spawning gravels are small. We manipulated the size of incubation gravels and egg size of Atlantic salmon ( Salmo salar) to test whether size-related entombment of larvae occurs. We find little evidence of size-related entombment, but we find evidence that gravel size does not affect all larval sizes equally. Larger larvae emerge from small gravels before development is complete and with a visible yolk sac, possibly due to oxygen limitation in small gravels. Smaller larvae always complete development in the gravel and emerge without a yolk sac. Although growth and survival may increase with juvenile size following yolk-sac absorption, juveniles with yolk sacs may fare worse when depredation rates are high. The egg size - gravel size correlation may therefore reflect increased postemergence mortality among larger offspring in small-gravel environments. Alternatively, compaction stress in fine gravels coupled with size asymmetries in larval strength may have caused the patterns that we observed, in which case our data may not help explain the egg size - gravel size correlation. [ABSTRACT FROM AUTHOR]

This study presents an assessment of the establishment success of smallmouth yellowfish, Labeobarbus aeneus (Burchell 1822), in the Great Fish River (GFRI), where they were introduced by the Orange-Fish River interbasin water transfer scheme and in the Glen Melville Reservoir (GMR), where the species was subsequently introduced from the GFRI. Edge Analysis of asteriscii validated an annual deposition rate of one growth increment per year and sampled fish were aged at between 0 and 10 years old. Combined sex length-at-age (Lt) was described by Lt = 650(l-e-0.066(t+4.22)) mm FL for GMR and Lt = 498 (l - e -0.23(t + 0.373) mm FL for GFRI. Natural mortality rate was estimated at 0.56/yr in GFRI and 0.96/yr in GMR. Condition factor was significantly higher in the GFRI than in GMR. In comparison with other populations, the GFRI population had reproductive and growth traits that were similar to those in its natural riverine range. Reproductive assessment showed ripe male and female fish in October to December in the GFRI, while in the GMIL ripe male fish but few ripe female fish were recorded. This was attributed to the lack of spawning cues in the reservoir. As a result, L. aeneus were considered established in the GFRI, but were not established and likely dependent on introductions in the GMR. [ABSTRACT FROM AUTHOR]

The article focuses on the study of protogynous sex change (female-male) which is relatively common life history pattern in fishes for which standard assessment methods do not exist. It cites the developed stock-assessment model for a commercially and recreationally exploited sex changing species to determine how ignoring or including sex change affects the assessment of the stock. However, it is found out that the stock assessment is not certain because of the unknown effect of male depletion in reproduction. The results of the study demonstrate that although incorporating sex change into stock assessment models is important and assessment of protogynous stocks also requires knowledge of the effect of male depletion on spawning potential and the factors that determine sex change.

Discerning population genetic structure is challenging for highly vagile open water animals, as contemporary gene flow may obscure historic phylogeographic patterns. We examined genetic variation among all 10 major river and reef spawning groups of walleye (Sander vitreus vitreus) in Lake Erie for evidence of isolation by distance, segregation by physiographic partitions, and natal site fidelity using 10 nuclear DNA microsatellite loci. Results revealed that although most spawning groups were distinguishable, relationships did not correspond with physiographic basins or distances among localities. Bayesian analyses showed connectivity among some southern shore spawning groups, which included the largest-sized groups. Significant genetic divergence was discerned among walleye spawning in the river systems of eastern Lake Erie, as well as in two sites in western Lake Erie, along with marked isolation from Lake St. Clair. Population structure of Lake Erie walleye thus appears to reflect the interaction of two different intrinsic factors: isolation due to natal site fidelity that maintains patterns of divergence, and connectivity due to individuals that stray from their natal sites to spawn. [ABSTRACT FROM AUTHOR]