Larger Juveniles Research Articles

Cichla cataractae (Cichliformes: Cichlidae), new species of peacock bass from the Essequibo Basin, Guyana and Venezuela

A new species of peacock bass, Cichla cataractae, is distinguished from all congeners by molecular evidence and unique patterns of adult and juvenile pigmentation. Juveniles (<150 mm SL) have sides of body dominated by a series of three conspicuous dark blotches with the one below soft dorsal fin largest, attenuated posteriorly (long teardrop shape) but distinctly separated from elliptical caudal blotch; same blotches eventually with pale border (ocellated) in largest juveniles. Adult pattern on sides dominated by two distinct dark blotches, each one ocellated; anterior blotch rounded, located below anterior base of spinous dorsal fin and not extending above anterior lateral line; posterior blotch highly irregular in shape, located below soft dorsal fin and often displaced dorsally; additional dark blotch below posterior base of spinous dorsal fin generally absent or small, ocellated or not, and level with anterior blotch; vertical bars on sides generally absent or faint; postorbital stripe always present, highly broken into irregular series of dark spots, each one usually ocellated. Cichla cataractae is endemic to the Essequibo Basin where it typically inhabits rocky shoals in river channels with swift current. new species is sympatric with the more widely distributed C. ocellaris, a species that prefers lentic habitats. Molecular analysis supports C. cataractae as a distinct lineage in a clade of Cichla containing C. temensis, C. melaniae, C. mirianae, C. piquiti and C. pinima. oldest extant specimens of the new species were collected by Carl H. Eigenmann in 1908 and documented in his seminal The Freshwater Fishes of British Guiana (Eigenmann, 1912).

Artisanal fishing activities and their documented interactions with juvenile white sharks inside a nursery area

Abstract Juvenile white sharks distribute in coastal nursery areas, which are essential for population growth. Bahía Sebastián Vizcaíno (BSV), Mexico, is a white shark nursery area in the north‐eastern Pacific. Despite existing regulations forbidding the capture of white sharks, incidental catches still occur in some areas. Artisanal fisheries constitute one of the most important economic activities in BSV, yet no formal description of either these fisheries or the incidental catch of juvenile white sharks exists due to the poor data reporting system, thus preventing a clear understanding of the implications of these catches for the white shark population of the north‐eastern Pacific. Artisanal fishing activities and their interactions with juvenile white sharks in BSV are described based on fishermen's knowledge. Artisanal fisheries in BSV are multi‐specific, targeting mostly bottom‐related species (e.g. white seabass and California halibut) that are also common prey for juvenile white sharks. These activities are the only source of income for the majority of fishermen in BSV and are conducted throughout the year, with gillnets being the main fishing gear. White sharks are incidentally caught in bottom gillnets mainly during the summer, although another peak in incidental catch was recorded during winter, possibly related to the presence of juvenile white sharks from California, USA. The most common size of juvenile white sharks incidentally caught was &lt;2 m in the nearshore areas close to the mouth of the Ojo de Liebre Lagoon; larger juveniles (~3 m) were caught in areas near Cedros, Natividad, and San Benito Islands. The multi‐specific nature of BSV artisanal fisheries and their socio‐economic value, and the high post‐release survival of juvenile white sharks suggest that future regulatory actions should focus on the release of incidentally caught live juvenile white sharks and the involvement of the BSV fishing community to increase the effectiveness of management efforts.

Attempted use of an uncommon bay scallop color morph for tracking the contribution of restoration efforts to population recovery

In our ongoing bay scallop restoration efforts in eastern Long Island, NY, United States, we have planted millions of hatchery‐reared juveniles to serve as broodstock when they mature. These plantings have driven the resurgence of larval recruitment, benthic population sizes, and commercial fishery landings over a 12‐year period. In this article, we detail an attempt to track the contribution of our restoration efforts to population rebuilding using planted “skunks,” an uncommon color morph, by looking for increased skunk frequencies in subsequent wild cohorts. Although we saw higher skunk frequencies among large juveniles in natural populations in the first 3 years after extensive skunk plantings, supporting use of uncommon color morphs as a passive tracer, this conclusion was not supported when examined over a 12‐year period, as no strong correlations were seen between skunk frequencies at different life stages (adult broodstock, small and large F1 juveniles, F1 adults) for respective cohorts. Potential reasons for poor correlation between skunk frequencies and restoration efforts include lower than expected production of skunk offspring, dilution of out‐planted contribution to growing natural populations, interannual variability in skunk frequencies that may have obscured the expected skunk signal, and/or differentially higher mortality of skunks at postset and larger juvenile stages. In the latter case, skunks experienced higher overwinter mortality, most likely due to predation, in 9 of 11 years. This led us to suspend skunk plantings after 3 years. Nevertheless, commercial fishermen perceived skunks to be “our” scallops, helping raise the profile of and support for our restoration efforts.

Characteristic changes in the population dynamics of asari (Manila) clam Ruditapes philippinarum in a period of stock decrease on the Banzu intertidal flat, Tokyo Bay

In Tokyo Bay, harvesting of asari (Manila) clam Ruditapes philippinarum has decreased since the early 2000s. In the present study, based on the abundance of sampled clams in four sites from 1998 to 2015 in the Banzu intertidal area, the authors discussed changes in the processes of population dynamics of asari clam which are possibly related to harvest decrease in Tokyo Bay. The findings are summarized as following two points. Firstly, the recent decline in the harvest of asari clams in Tokyo Bay may be caused by the mortality of benthic juveniles. The spatial density of juvenile clams at recruitment showed a varied increase during the study period. In contrast, from the recruitment to adult stages, the mortality coefficient z and von Bertalanffy growth function k consistently increased and decreased, respectively. Moreover, decreasing trends in the spatial density of adult clams were apparent in the concurrent period. Thus, the decrease of adult clams was suggested to be due to poor survival in juvenile clams after recruitment. Secondly, the depletion of the autumn cohort and spatial relocation of the large juveniles were apparent after 2009. The autumn cohort significantly decreased in size-frequency composition, despite the increased abundance and size of juvenile clams at recruitment after 2009. Referring to recent reports, predation by fish may be one of the processes that depleted the abundance of the autumn cohort. Additionally, the density of year-class cohorts increased for 2–4 months from their first appearance to the completion of recruitment, which was likely due to the spatial immigration of large juveniles into the study area. The physical stress of sea water movement caused by increasing strong wind may have encouraged the spatial transport of the juveniles. The depletion of the autumn cohort and spatial immigration of the large juveniles were temporally overwrapped with the period of an outbreak and continuing infestation of the parasitic sea spider Nymphonella tapetis after 2007. This observation can hypothesize that poor burrowing activity due to the parasitic infestation allowed the clams to suffer predation or passive transport. However, above changes in population dynamics after the late 2000s cannot be solely connected to decline of asari harvest, because that decrease in the harvest of asari clams in Tokyo Bay began in the early 2000s; there remain factors other than this one that may have acted on the stock decline after the early 2000s in Tokyo Bay.

Does proximity to freshwater refuge affect the size structure of an estuarine predator (Carcharhinus leucas) in the north-western Gulf of Mexico?

The life histories of estuarine species are often adapted to the environmental variability they experience. However, estuaries are increasingly vulnerable to natural and anthropogenic changes, necessitating an understanding of how shifting conditions affect the survival, behaviour and population structure of estuarine-dependent animals. In this study we used data from fisheries-independent surveys collected across six estuaries with variable salinity regimes in Texas, USA, from 1975 to 2016 to investigate the role sources of freshwater inflow play in shaping juvenile bull shark Carcharhinus leucas size structure. High frequencies of co-occurrence with similarly sized conspecifics (59% of capture events) suggest bull sharks segregated within Texan estuaries based on body size. Bull shark sizes increased with distance to the nearest source of freshwater inflow, although effect sizes were small and access to freshwater habitats may be more important in shaping size-dependent distribution patterns. River mouths were disproportionately used by smaller juveniles (&amp;lt;90-cm total length, TL) and avoided by larger juveniles (&amp;gt;135cm TL). However, the use of river mouths decreased in estuaries characterised by limited freshwater inflow and greater variability in salinities at river mouths, highlighting geographic differences in the functions these habitats provide as potential environmental and predator refugia. Young-of-the-year (i.e. age-0) sharks also increased their use of river mouths throughout the 40-year study period, revealing the growing importance of river mouths as potential nursery habitats.

Feasibility of early outplanting of sexually propagated Acropora verweyi for coral reef restoration demonstrated in the Philippines

Over the last 20 years, coral sexual propagation techniques for reef restoration have been steadily developed and improved. However, these techniques involve considerable time and costs to grow coral propagules. There is a need to examine the optimal size of juvenile corals for outplantation. Here, we outplanted sexually propagated small (3–5 mm diameter) and large (10–15 mm diameter) Acropora verweyi corals at 4 months after fertilization at two sites in northwestern Philippines, and compared their survival and radial growth rate after a year. A. verweyi coral juveniles (n = 240) exhibited an overall mean survival of 29.5% and growth rate of 11.12 ± 6.2 mm/year (mean ± SD). Large colonies had a significantly higher growth rate than smaller colonies. Although survivorship of large juveniles was significantly better than that of the smaller ones at one site, it did not differ significantly at the other. Each 4‐month‐old coral cost US$1.52 to produce, while the cost of each of the outplanted juveniles (n = 240) was about US$2.67, whereas the cost of each survivor about a year after outplantation was US$11.47. Results suggest that A. verweyi reared in ex situ nurseries for only 4 months can survive reasonably well when outplanted onto coral reefs.

The tolerance of juvenile stone crabs to hypoxia: Size matters

Over the last fifty years, anthropogenic activities have increased nutrient loading into coastal habitats causing more frequent hypoxic events. Global climate change is expected to increase the frequency and severity of hypoxic conditions as temperatures continue to increase, which will pose physiological and metabolic limits on many coastal species. This study determined the survivorship and tolerance of the commercially important juvenile stone crab (Menippe mercenaria) during short-term hypoxic exposure under laboratory conditions. Small (2.0–3.0 mm carapace width) and large (5.0–18.0 mm carapace width) juveniles were gradually exposed to moderate hypoxic conditions (1.5 mg L−1 oxygen concentration) for 2 h and compared to individuals in normoxic conditions. Smaller juveniles were more sensitive than larger conspecifics and exhibited 80% mortality. Larger juveniles did not exhibit significant mortality (~12% total mortality); however, 35% of the larger crabs displayed immobile by the end of the experiment. These results indicate that juvenile stone crab tolerance to hypoxia is size-dependent and likely changes throughout ontogeny.

Testing adaptive hypotheses on the evolution of larval life history in acorn and stalked barnacles.

Despite strong selective pressure to optimize larval life history in marine environments, there is a wide diversity with regard to developmental mode, size, and time larvae spend in the plankton. In the present study, we assessed if adaptive hypotheses explain the distribution of the larval life history of thoracican barnacles within a strict phylogenetic framework. We collected environmental and larval trait data for 170 species from the literature, and utilized a complete thoracican synthesis tree to account for phylogenetic nonindependence. In accordance with Thorson's rule, the fraction of species with planktonic‐feeding larvae declined with water depth and increased with water temperature, while the fraction of brooding species exhibited the reverse pattern. Species with planktonic‐nonfeeding larvae were overall rare, following no apparent trend. In agreement with the “size advantage” hypothesis proposed by Strathmann in 1977, egg and larval size were closely correlated. Settlement‐competent cypris larvae were larger in cold water, indicative of advantages for large juveniles when growth is slowed. Planktonic larval duration, on the other hand, was uncorrelated to environmental variables. We conclude that different selective pressures appear to shape the evolution of larval life history in barnacles.

Ontogenetic change in the amount and position of slow-oxidative myotomal muscle in relationship to regional endothermy in juvenile yellowfin tuna Thunnus albacares.

Myotomal slow-oxidative muscle (SM) powers continuous swimming and generates heat needed to maintain elevated locomotor muscle temperatures (regional endothermy) in tunas. This study describes how the amount and distribution of myotomal SM increases with fish size and age in juvenile yellowfin tuna Thunnus albacares in relationship to the development of regional endothermy. In T. albacares juveniles 40-74 mm fork length (LF ; n = 23) raised from fertilised eggs at the Inter-American Tropical Tuna Commission Achotines Laboratory in Panama and larger juveniles (118-344 mm LF ; n = 5) collected by hook and line off of Oahu, Hawaii, USA, SM was identified by histochemical staining for the mitochondrial enzyme succinic dehydrogenase or by colour (in the two largest individuals). The cross-sectional area of myotomal SM at 60% LF , a position with maximal percentage of SM in larger T. albacares, increased exponentially with LF . The percentage of total cross-sectional area composed of SM at 60% LF increased significantly with both LF and age, suggesting that SM growth occurs throughout the size range of T. albacares juveniles studied. In addition, the percentage of SM at 60% LF that is medial increased asymptotically with LF . The increases in amount of SM and medial SM, along with the development of the counter-current heat-exchanger blood vessels that retain heat, allow larger tuna juveniles to maintain elevated and relatively stable SM temperatures, facilitating range expansion into cooler waters.

Dietary ontogeny of the blue shark, Prionace glauca, based on the analysis of δ13C and δ15N in vertebrae

Ontogenetic changes in habitat and food preferences are common in nature; they reflect changes in the needs of organisms during their lifetime. Studying the dietary ontogeny of pelagic species is a difficult task, because of migratory processes and the inaccessibility of their habitats. As a result, their life history remains poorly understood, or even unknown. Here, we studied the dietary ontogeny of 18 blue sharks, Prionace glauca, using isotopic analysis in vertebrae. A total of 132 samples of vertebral collagen were taken (64 from males and 68 from females). The wide range of δ13C values (− 16.8 to − 13.1‰) suggests that these sharks use both coastal and oceanic areas for feeding. Small juveniles and adults preferred coastal areas, while medium-sized and large juveniles preferred oceanic areas. The estimated δ15N values (9.5–19.0‰) suggest that P. glauca is a top predator that occupies various trophic levels and/or it feeds across areas with different baseline δ15N (trophic position 3.9–8.4). Isotopic enrichment and differences in δ13C and δ15N thus suggest ontogenetic changes in habitat use and prey consumption between maturity stages. The use of hard anatomical structures (vertebrae) is highly relevant because they integrate information on the dietary ontogeny of this shark species.

Limulus polyphemus (Atlantic Horseshoe Crab) Habitats in a Small Estuary and the Adjacent Inner Continental Shelf: Linkages Across Mid-Atlantic Bight Seascapes

While there are numerous studies of Limulus polyphemus (Atlantic Horseshoe Crab) populations on the East and Gulf coasts of the US, especially for spawning adults in large estuaries such as Delaware Bay, there are fewer efforts relative to small estuaries in the Mid-Atlantic Bight. We determined, for the first time, the pattern of seasonal linkages between the Great Bay–Little Egg Harbor estuaries in southern New Jersey and the adjacent inner continental shelf with multiple gears over multiple years. Adults of both sexes are distributed along the inner continental shelf in all seasons, while large juveniles were most abundant in the fall. The seasonal occurrence of larvae, small juveniles, and spawning adults in high salinity, sandy, natural habitats in these small estuaries was consistent. Our findings suggest that these and other small estuaries may provide the same habitats, predators, prey, and fishery resources as larger estuaries, except at a smaller scale. Thus, small estuaries contribute by enhancing landscape and habitat diversity for this vulnerable species. Further clarification of the importance of estuarine habitats would benefit from an increasing emphasis on juveniles and their subsurface habitats in small and large estuaries.

The existence of a fire‐mediated tree‐recruitment bottleneck in an Asian savanna

AbstractAimA considerable proportion of the global savanna biome has been mis‐classified as forest, especially in Asia. However, the structure and responses of dominant tree species to fire can help to clarify this ambiguity. Here, we examine demographic structure and fire responses of four dominant tree species in a deciduous dipterocarp forest (DDF) of the continental Southeast Asia. We examine whether fire creates a tree‐recruitment bottleneck in the DDF, as in savannas on other continents.LocationYokDon National Park, Vietnam.TaxonDipterocarpus tuberculatus Roxb.; Dipterocarpus obtusifolius Teysm. ex Miq.; Shorea obtusa Wall. ex Blume; Shorea siamensis (Kurz) Miq.MethodsWe measured the size of all 8,288 individuals of the four dominant dipterocarp species in 12 pair study sites. We then applied fire treatments (burnt or unburnt) to the plots and monitored the survival and growth of juveniles five times over the subsequent growing season.ResultsAll four species showed clear indications of a recruitment bottleneck at the sapling stage. Almost all juveniles in the burnt plots suffered aboveground mortality, but 64% resprouted by the end of the following growing season. Compared to large juveniles, small juveniles had a significantly higher probability of aboveground mortality and a more limited ability to resprout. Within 3 months of fire, 43%–93% of individuals had resprouted, and they had recovered 67%–95% of their pre‐fire basal diameter and 43%–94% of their pre‐fire height. At the end of the post‐fire growing season, burnt juveniles experienced virtually no net increase in size; however, juveniles in unburnt plots attained up to 150% of their pre‐fire size.Main conclusionsThe four dominant tree species of the DDF show remarkable similarities in the demographic structures and fire‐responses with savanna tree species on other continents. Our results are consistent with the notion that the DDF is functionally similar to savannas on other continents. Fire appears to act as potent environmental filter of tree species composition in the DDF.

Ontogenetic Habitat Usage of Juvenile Carnivorous Fish Among Seagrass-Coral Mosaic Habitats

Seagrass beds and coral reefs are both considered critical habitats for reef fishes, and in tropical coastal regions, they often grow together to form “mosaic” habitats. Although reef fishes clearly inhabit such structurally complex environments, there is little known about their habitat usage in seagrass-coral mosaic habitats. The goal of this study was to examine potential factors that drive habitat usage pattern by juvenile reef fishes. We quantified (1) prey availability, (2) potential competitors, and 3) predators across a gradient of mosaic habitats (n = 4 habitat types) for four dominant carnivorous fishes (lethrinids and lutjanids) in the main recruitment season at Dongsha Island, South China Sea. We found that the coral-dominated habitats had not only a higher availability of large crustacean prey but also a higher abundance of competitors and predators of juvenile fishes. Food availability was the most important factor underlying the habitat usage pattern by lethrinids and lutjanids through ontogeny. The predation pressure exhibited a strong impact on small juvenile lethrinids but not on larger juveniles and lutjanids. The four juvenile fishes showed distinct habitat usage patterns through ontogeny. Collectively, mosaic habitats in the back reef system may be linked to key ontogenetic shifts in the early life histories of reef fishes between seagrass beds and coral reefs.

How Far Upstream: A Review of Estuary-Fresh Water Fish Movements in a Large Neotropical Basin

The present study comprises the first systematic record of upstream migratory limits for estuarine migratory fish species of the Patos Lagoon basin (Southern Brazil). The Sinos River sampling program included 85 sites sampled from 2004 to 2015, covering lowland stretches and headwaters. The Guaiba sampling program was performed from February 2011 to March 2013, comprising 59 independent samples. Six estuarine migratory fish species are present in upper Patos basin, covering distances in the range of 250-450 km from the Patos Lagoon inlet with the Atlantic Ocean. Parapimelodus nigribarbis comprised animals in the range of 11.3 to 18.9 cm (Median=13.3 cm), corresponding to adult individuals (Sinos: n=459; Guaiba, n=149). The species was captured almost 500 km from the Patos inlet, reaching 180 km upstream in the Sinos main channel. In the Guaiba lake, the species was captured mainly in autumn, although more abundant in Sinos River in winter and spring. Most of Micropogonias furnieri individuals (n=63) were juveniles (10.7-33.4 cm, median=14.2 cm). The species was not captured in Sinos basin. In the Guaiba Lake the species occurred predominantly in the southernmost part (downstream) and was more abundant (>10x) during the winter. Lycengraulis grossidens was captured in Sinos basin restricted to low stretches in summer/spring months (n=7). In the Guaiba Lake (n=134) the species presented widespread distribution all over the lake surface and year around, although ten times more abundant in spring. The majority of the specimens were adults (8.2-26.9cm, median=20.0 cm). Genidens genidens (n=27) was captured only in summer in the southern (downstream) part of the Guaiba Lake. Most individuals were adults (24.5-34.0 cm, median=27.8 cm). Genidens barbus (n=7) was restricted to spring-summer months and was captured only on southern (downstream) segments of the Guaiba Lake, comprising mainly large juveniles and adults (31.5 – 68.0 cm, median=37.9). Mugil liza appeared in spring in relative low abundances (n=13) but was widespread in the entire Guaiba Lake during the summer. The species was not captured in Sinos sampling program. Size profile comprise specimens in the borderline of maturity (34.3-45.5 cm, median=38.9 cm). General descriptive models for fish displacement in the basin are presented.

Adhesive force and endurance during waterfall climbing in an amphidromous gobiid, Sicyopterus japonicus (Teleostei: Gobiidae): Ontogenetic scaling of novel locomotor performance

An amphidromous sicydiine goby, Sicyopterus japonicus, exhibits rock-climbing behavior during upstream migration along rivers and streams. Using a pelvic sucker formed by fused pelvic fins, S. japonicus generates suction adhesion on the climbing surface. By measuring performance variables that correlate with successful rock-climbing capability, we evaluated scaling relationships of adhesive suction force generated by the pelvic sucker and fatigue during climbing in S. japonicus during ontogeny. In continuous climbing on the experimental 60°-inclined surface, the pelvic sucker of S. japonicus exhibited strong positive allometry in generating suction force for adhesion during ontogeny. In contrast, fatigue time of the pelvic sucker muscles for sustained adhesion scaled non-linearly with body mass during ontogeny. In addition, fatigue time and body mass showed the best fit to a quadratic regression, which predicted intermediate-sized individuals (large juveniles to small adults) to have better performance in adhesive endurance than smaller or larger individuals. Our experimental results indicate that different sizes of waterfall-climbing gobies have different performance capacities for rock climbing perhaps because of physiological differences in their pelvic muscles. In addition, our data from S. japonicus indicates that selection pressures on the locomotor capacities of waterfall-climbing gobiids vary during ontogeny.

Movement of juvenile barramundi (Lates calcarifer) through a cone ramp fishway at a modified coastal wetland in central Queensland, Australia

Barramundi (Lates calcarifer) often migrate from marine to fresh water as juveniles. In March 2018a relatively large number of small juveniles (&amp;lt;100mm) were recorded moving through a fishway on a tidal interface barrier in central Queensland, Australia. This is in contrast to the few documented observations of transitional movements, which involved mostly larger juveniles (250–400mm).

The snakehead fish Channa aurolineata is a valid species (Teleostei: Channidae) distinct from Channa marulius.

Channa aurolineata is a valid species of the Marulius group. Previously treated as a synonym of C. marulius, C. aurolineata is readily distinguished from C. marulius by a different colour pattern, in which a conspicuous white posterior margin is present on the black scales that form the dark lateral blotches in larger juveniles and adults (vs. scales without white margin but with white spots in C. marulius). Channa aurolineata also differs from C. marulius by having more lateral line scales (65-71 vs 62-65), more dorsal-fin rays (55-58 vs 52-56) and more vertebrae (63-66 vs 59-63). In addition to these morphological differences, C. aurolineata is genetically more than 8% different (uncorrected p-distance) from C. marulius at the COI barcoding gene, a difference consistent with levels of genetic divergence observed among different species. The same characters that distinguish C. aurolineata from C. marulius also distinguish it from C. pseudomarulius, the other Indian member of the Marulius group. Channa aurolineata has a widespread distribution in larger rivers in Myanmar, including the Chindwin, Ayeyarwaddy, Sittaung and Thanlwin river basins. The Indo-Burman ranges appear to delineate the western geographical limit of this species, with C. marulius restricted to the western side of this mountain chain.

Description of juvenile specimens of Prosaurolophus maximus (Hadrosauridae: Saurolophinae) from the Upper Cretaceous Bearpaw Formation of southern Alberta, Canada, reveals ontogenetic changes in crest morphology

ABSTRACTThree juvenile specimens of Prosaurolophus maximus, represented by articulated to disarticulated skeletons, are the smallest known individuals for the taxon. Cranial anatomy of the juvenile specimens indicates that diagnostic characters of P. maximus are ontogenetically variable. In the smallest individual, the crest and deeply excavated fossa at the caudal margin of the circumnarial depression are poorly developed or absent. The crest approaches adult-like morphology in large juveniles, whereas crest robusticity and the deep excavation of the circumnarial depression occur only in subadult and adult individuals. The shape of the caudal margin of the circumnarial depression is consistent between juvenile and adult individuals, potentially making this feature a reliable character for taxonomic identification at younger ontogenetic stages. The crest of P. maximus grows isometrically during ontogeny, unlike the positive allometric growth of lambeosaurine hadrosaur crests, suggesting that this taxon may have had soft tissue structures associated with the narial-crest region, rather than the bony crest itself, selected for sexual display. Recovered from sediments of the Bearpaw Formation deposited during the Baculites compressus ammonite zone and magnetochrons 33n.3n to 33n.2n, the juvenile specimens are stratigraphically younger than P. maximus specimens from the Dinosaur Park Formation (Alberta) and contemporaneous with most specimens from the Two Medicine Formation (Montana), extending the temporal range of the taxon to 75.7–74 Ma. The occurrence of P. maximus in well-drained terrestrial deposits of the Dinosaur Park and Two Medicine formations and marine sediments of the Bearpaw Formation indicates that this taxon inhabited various paleoenvironments in western North America.

Evaluation of the growth and survival rate of the Caribbean Sea cucumber, Isostichopus badionotus (Selenka, 1867), early juveniles produced in captivity

Isostichopus badionotus is a new commercially important sea cucumber in the Caribbean that has rapidly shown signs of overexploitation. There is no information on the growth and survival rates for wild or hatchery‐produced early juveniles. Hatchery production and determination of juvenile growth rates are essential for future aquaculture efforts for this species. In this study, daily growth rate (GR), specific growth rate (SGR), weight gain (WG), survival rate (SR), and weight–length relation (WLR) were evaluated using small (0.01 g) and large (0.25 g) hatchery‐produced early juveniles under laboratory conditions. Growth was rapid compared to other cultured sea cucumber species; maximal values of SGR and WG were obtained for small juveniles (4.58%/day and 2,191%, respectively), while maximal GR and SR were obtained for large juveniles (0.29 mm/day and 99.17%, respectively). A wide range of sizes was evident at the end of each trial. The WLR of small and large juveniles fit with a negative allometric growth trend. This study highlights the potential production of I. badionotus as early juvenile stages withstand hatchery handling well and exhibit a high SR, reaching commonly released mean sizes (&gt;0.7 g and 25 mm) after almost 3 months (120 days postfertilization).

Effect of transfer time, temperature, and size on burrowing capacity of juvenile clams, Mulinia edulis, from hatchery

Studies under laboratory and field conditions have shown that juvenile Mulinia edulis clams measuring 5–15 mm are able to tolerate transfer times of over 24 hr and burrow successfully. Burrowing generally followed an asymptotic curve over time, with a rapid initial phase for smaller juveniles, which slowed over time. In laboratory conditions, at low temperatures (8°C), juvenile burrowing was initially rapid (50–70% at first 2 min). In summer temperatures (15.5°C), the burrowing capacity of three sizes of juvenile clams was tested. Size determines differences in burrowing dynamics, where juveniles of 8.9 mm shell length (SL) take longer to burrow than smaller juveniles (4.9 and 6.3 mm SL). For longer transfer times in laboratory conditions (&gt;12 hr), burrowing was slower. The results indicate a faster burrowing rate in smaller (&lt;10 mm) juvenile clams than in larger ones. Transfer times over 24 hr in field experiments show burrowing levels of over 50% after a 60‐min evaluation, with larger juveniles (&gt;10 mm) requiring longer for burrowing. Based on our results, we suggest sending seeds out to grow in natural environments at SL &lt;10 mm, temperatures below 12°C, and transfer times shorter than 12 hr. These results are valuable for improving future transfer techniques from hatchery to growout for small‐scale aquaculture of this new native species in South America.