Aquaculture potential of the basket cockle (Clinocardium nuttallii). Part 1: effects of stocking density on first year grow‐out performance in intertidal and off‐bottom suspended culture

The basket cockle (Clinocardium nuttallii) is a candidate species for aquaculture in the northeast Pacific. The aim of the current research was to assess the feasibility of C. nuttallii grow‐out, with an emphasis on growth performance and qualities affecting product marketability. In this article, we investigated the combined effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (1500, 3000, 10 500 and 21 000 ind m^?2) on C. nuttallii survival and growth during the first year of grow‐out (May through October). In intertidal culture, cockles exhibited low survival and poor growth rates. In suspended culture, survival was consistently high (>96%) at all stocking densities tested; growth and condition parameters had the highest values at 1500 and 3000 ind m^?2. The edible portion (meat yield) exceeded 40% of the whole wet weight at all stocking densities, occurrences of fouled and deformed cockles were <1% and no commensal species were observed. Depending on the minimum harvestable size and stocking density chosen, harvestable proportions constituted from 1.1% to 15.2% by October of the first grow‐out year in the suspended system. The effects of stocking density and depth on second year grow‐out performance of C. nuttallii are reported in a companion paper (Dunham et al. in this issue).     

Aquaculture potential of the basket cockle (Clinocardium nuttallii). Part 2: effects of stocking density and depth on second year grow‐out performance of three size cohorts in intertidal and off‐bottom suspended culture

We investigated the effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (5%, 10%, 35% and 70% bottom cover) on survival, growth and condition indices of three size cohorts (16, 22 and 32 mm initial shell length) of the basket cockle, Clinocardium nuttallii, during a second year of grow‐out. In addition, we evaluated the effects of depth (2, 4 and 6 m) in suspended culture. All size cohorts demonstrated significantly higher growth rates, soft‐tissue biomass and condition indices in the off‐bottom suspended system compared to the intertidal one. In suspended culture, however, C. nuttallii exhibited sub‐optimal survival, shell deformities and heavy fouling. For all size cohorts, stocking density had a significant effect on most growth and condition parameters, except meat yield indices, in both culture modes. An initial maximum stocking density of 10% cover is recommended for all size cohorts. Culture depth did not have a consistent statistically significant effect on any of the growth or condition parameters. Depending on the grow‐out scenario, stocking density and harvestable size chosen, the cumulative harvestable proportion after the second year of grow‐out constituted 15.5–63.1% of the seed planted. Our results could be used to develop and improve culture techniques for C. nuttallii and other cockle species.     

Effects of mono‐species and bi‐species microalgal diets on the growth,survival and metamorphosis of auricularia larvae of the California sea cucumber,Parastichopus californicus (Stimpson, 1857)

The effects of mono‐species and bi‐species microalgal diets on body length, survival and metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus, were tested in two separate laboratory feeding experiments. The first examined eight single species of microalgae – Chaetoceros calcitrans (Cc), Chaetoceros muelleri (Cm), Dunaliella tertiolecta (Dt), Isochrysis sp. (Tahitian strain: TISO) (Ti), Pavlova lutheri (Pl), Phaeodactylum tricornutum (Pt), Tetraselmis suecica (Ts) and Thallassiosira pseudonana (Tp). The second experiment took the five most effective single species from the first experiment (i.e. Cc, Cm, Dt, Pl and Ti) and presented them in all possible binary combinations. In the first experiment, Cc was determined to be the best diet on the basis of generating a significantly higher metamorphic rate (65.5 ± 4.2%, mean ± SD) than any other species and leading to one of the best survival rates (72.3 ± 7.6%) and greatest body lengths (831.6 ± 5.6 μm at day 14). In the second experiment, diets containing Cc generally produced the highest survival and metamorphic rates and greatest body lengths (except Cc/Cm) of all mixed diets, although no bi‐species treatment was ever significantly superior to a control of Cc alone. Of the various mono‐species and bi‐species diets evaluated for rearing auricularia larvae of P. californicus, Cc (either alone or mixed with other species) is recommended.     

Effect of ration on gonad development of the Pacific geoduck clam,Panopea generosa (Gould, 1850)

The effect of ration on Panopea generosa gonad development was tested over 52 days. Clams were fed Isochrysis sp. and Chaetoceros muelleri (50 : 50 cell count) at rations of 0.8 × 10⁹, 2.4 × 10⁹, 4.0 × 10⁹, 5.6 × 10⁹, 7.2 × 10⁹ and 10.0 × 10⁹ cells clam^?1 day^?1 (R₁, R₂, R₃, R₄, R₅ and R₆, respectively). The highest ration (R₆) caused a 25% die‐off within 3 days and was discontinued. Ration did not significantly affect condition index, gonadosomatic index, connective tissue occupation index or oocyte diameter. Clams fed the R₅ ration (85% of which spawned from day 26 to 52) were more spent than clams in any other treatment with significantly fewer oocytes mm^?2 than those fed the R₁, R₂ and R₃ rations and significantly lower levels of sperm occupation than clams fed any other ration. Spawn percentages were low from day 26 to 52 in R₁, R₂ and R₄ (15, 0 and 0%, respectively). Clams in the R₃ treatment had a similar spawn percentage (100% from day 26 to 52) to those in the R₅ treatment yet maintained gonads in a more ripened condition with higher levels of gamete occupation, making R₃ the most likely ration to maximize gamete output over time.     

Decomposition of Pinus radiata coarse woody debris in New Zealand

The decomposition of Pinus radiata (D. Don) stems, coarse woody roots and stumps was studied in Tarawera forest, Bay of Plenty region, North Island, New Zealand. The study examined the residues from two thinning events with 6 and 11 years of decay. Changes in the mass of stems, and density of roots and stumps were used to estimate the decay rate constants using a single exponential model. The decay rate of stems was not significantly related to DBH and averaged 0.1374 year⁻¹ (22 years for 95% mass loss). The decay rate of coarse woody roots was not significantly different to stem decay and averaged 0.1571 year⁻¹ (19 years for 95% mass loss). A large range in stump decay rates was measured and a significantly lower decay constant was observed for stumps (0.1101 year⁻¹, 27 years for 95% mass loss), possibly due to the stumps being kept alive after felling through root grafting and a resistance to decay due to the presence of resin. The concentration of C remaining in stems and stumps increased with mass loss from 52% to 55% C after 11 years of decay. The C concentration in coarse woody roots initially increased but then declined near to the original level of 50% after 11 years of decay. Nitrogen concentrations increased substantially in all components with decay.     

Effects of supplementation of medium with different antioxidants during in vitro maturation of bovine oocytes on subsequent embryo production

The aim of this study was to assess the effects of different antioxidants on the levels of reactive oxygen species (ROS) and glutathione (GSH) in oocytes during in vitro maturation (IVM), as well as on the production of embryos. Oocyte of slaughterhouse‐derived cattle ovaries were placed in IVM with different antioxidants: quercetin (2 μM), cysteamine (100 μM), carnitine (0.5 mg/ml), vitamin C (50 μg/ml) or resveratrol (2 μM). Oocytes matured without any antioxidant supplementation were used as control. The oocytes were assessed for maturation rates and for ROS and GSH levels by fluorescence staining in 2′,7′‐dichlorodihydrofluorescein diacetate and Cell Tracker Blue, respectively. Embryo production was assessed in terms of cleavage, blastocysts and hatching rates and embryo cell numbers. The results expressed in arbitrary fluorescence units showed ROS reduction (p < .05) in the groups with quercetin (27.5 ± 3.4), vitamin C (27.1 ± 3.0) or resveratrol (28.1 ± 4.7), in comparison with those with cysteamine (34.9 ± 4.5), carnitine (34.6 ± 3.8) or to the control group (36.5 ± 5.2). GSH levels increased (p < .05) in cysteamine (63.5 ± 5.5) or carnitine (60.8 ± 4.4) groups in comparison with quercetin (52.7 ± 5.1), vitamin C (53.0 ± 3.8), resveratrol (53.1 ± 4.4) or to the control (49.6 ± 4.5). Nuclear maturation cleavage and hatched blastocysts rates did not differ (p > .05) between groups. However, blastocyst rates after in vitro fertilization in quercetin (53.5 ± 3.9%), vitamin C (52.1 ± 3.1%) resveratrol (54.2 ± 4.0%), cysteamine (52.4 ± 2.7%) or carnitine (54.2 ± 3.1%) groups were higher (p < .05) than in the control (47.2 ± 2.7%). Total cell numbers in embryos from the vitamin C, resveratrol, cysteamine or carnitine groups were higher than in quercetin and control groups, which were similar to each other. The results suggest that using antioxidants during IVM may reduce oxidative stress either by decreasing ROS levels directly or by increasing GSH levels in oocytes, depending on the type of antioxidant used. Overall, oxidative stress control during IVM with the antioxidants examined here improved blastocyst development with similar efficacy.     

Prioritizing avian conservation areas for the Yellowstone to Yukon Region of North America

Prioritizing new areas for conservation in the Rocky Mountains of North America is important because the current intensity and scale of human development poses an immediate threat to biodiversity. We identified priority areas for avian biodiversity within a 3200-km corridor from Yellowstone National Park in Wyoming, US to the Yukon in Canada (the Y2Y region). We applied the conservation planning tool, MARXAN, to summarize 21 avian values. MARXAN minimizes the area delineated, while simultaneously incorporating multiple criteria (species richness representation, spatial clustering) and biodiversity targets into a single mappable solution. We prioritized avian biodiversity ‘hotspots’ at continental and ecoprovincial scales based on: (1) avian species richness; and (2) habitat associations of 20 focal species. At the continental scale, the single best solution represented 19% of the Y2Y region; 29% of this solution overlapped with existing protected areas. In northern Y2Y, large contiguous areas with high avian value were concentrated on the western edge of the continental divide. In southern Y2Y, contiguous areas were smaller and more numerous than in the north. In contrast to the majority of studies prioritizing conservation areas, we explored the effect of varying the extent of the target region by analyzing data at the scale of the entire Y2Y region and for eight ecoprovinces separately. We found that (1) large contiguous patches characterized only three ecoprovinces, while for the remaining ecoprovinces, numerous single scattered habitat patches of varying sizes were required to meet conservation goals; and (2) generally, only a small percentage of sites was already protected within the existing protected areas network. Our results are important for conservation planners and resource managers in the Y2Y region for incorporating areas of high conservation value for birds at regional and ecoprovincial scales during conservation project design and adaptive planning.     

Effects of stocking density and substratum on the survival,growth, burrowing behaviour and shell morphology of juvenile basket cockle,Clinocardium nuttallii: implications for nursery seed production and field outplanting

The basket cockle, Clinocardium nuttallii, is a candidate species for aquaculture in British Columbia, Canada. Previous research on broodstock conditioning, embryonic development and larval rearing of C. nuttallii demonstrated the potential for reliable hatchery production of cockle seed. In this paper, we investigated the effects of culture density (50% and 150% bottom cover in a monolayer) and substratum (none and fine sand) on cockle seed survival, growth, behaviour and shell morphology to improve the efficiency of the nursery production phase. Low stocking density (50% cover) yielded a shell length increase from 3 to 7 mm over a 4‐week period. High stocking density (150% cover) negatively impacted some of the growth and condition parameters studied, but did not have a statistically significant effect on seed survival. Growing seed without substratum did not significantly affect seed survival or growth, but led to shell deformities (at shell length >15 mm) and lower burrowing rates when cockles were subsequently placed on sand. We recommend planting seed for grow‐out at a shell length not exceeding 15 mm. Acclimating seed to the substratum before planting may increase the burrowing rates, thereby reducing the risks of seed dislocation and mortality. Additional studies are required to determine optimal substratum acclimation times and techniques.     

Catching invasive Chinese mitten crabs while releasing the endangered European eel and other fish by‐catch: The implications of fyke net design

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