Influence of intra- and interspecific competition on periphyton biomass and growth performance of Holothuria scabra juveniles

The effects of sea cucumber (Holothuria scabra) juvenile density and interspecific competition from the opisthobranch Stylocheilus striatus (SS) on periphyton biomass and growth performance of H. scabra (HS) were assessed. The number of H. scabra juveniles (15, 50, 100) in net enclosures (treatments HS15, HS50, and HS100) was varied and feeding activity of S. striatus was assessed at a density of 15 individuals per net enclosure (treatment SS15), and in co-culture with H. scabra (treatment HS15/SS15). A control treatment without H. scabra or S. striatus was included in the 28-d experiment. Highest and lowest growth rates of H. scabra occurred in the lowest (HS15) and highest (HS100) stocking density treatments, respectively, on days 14 and 28. Growth of H. scabra juveniles in the HS15 treatment was more than double that of those in the HS15/SS15 treatment. Juvenile survival was significantly higher in the HS15 treatment on days 14 and 28, but did not differ significantly from that of juveniles in the HS15/SS15 and HS50 treatments on day 14. Grazing activity of sea cucumber juveniles and S. striatus resulted in a decline in periphyton biomass (AFDW) after day 7. Differences in food consumption (based on faecal production) among treatments were significant only on days 1 and 21 with the greatest consumption (17.5 mg periphyton ind−1 d−1) by S. striatus in the SS15 treatment. Holothuria scabra juveniles in the HS15 treatment consumed 4.9 mg ind−1 d−1, while those in the HS100 treatment consumed only 1.8 mg ind−1 d−1 after 24 hrs.

Recreational fisheries as a driver of salmonid population conservation

ABSTRACTThe need to monitor and protect biodiversity has never been greater, yet resources are often constrained economically. The ecosystem service paradigm could promote nature conservation while sustaining economic activity and other societal benefits, but most efforts to assess biodiversity-ecosystem service (B-ES) links have focused on diversity measures, with little attention on how species abundance relates to the magnitude of ES provision.Here, we utilised four national scale, multi-decadal, Atlantic salmon (Salmo salar) datasets to investigate links between juvenile density, the abundance of returning adults, and two measures of recreational angling provision: rod catches and angling effort.Recreational rod catches only tracked juvenile density and returning adult numbers in catchments where juvenile and adult numbers were decreasing, implying important early-warning of ES decline. In contrast, angling effort declined consistently through time.Synthesis and applications. These data illustrate i) the difficulty in measuring ES in ways that explicitly relate human resource use to nature conservation, and ii) the need for better quantification of populations at all life stages that determine ES provision, particularly in species where long-distance movements bring exposure to multiple global pressures. We suggest additional opportunities (e.g., monitoring of smolts, eDNA and citizen science initiatives) to facilitate conservation efforts and increase capacity to monitor ecosystem service sustainability.

SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS

Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.

SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS

Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.

Implications of spatial contraction for density dependence and conservation in a depressed population of anadromous fish

Changes in density-independent mortality can alter the spatial extent of populations through patch extinction and colonization, and spatial contraction may alter population productivity and compensatory capacity. Here, we analyze a time series of steelhead (Oncorhynchus mykiss) abundance and examine the hypothesis that spatial contraction can decrease compensatory capacity. Over the last 20 years, steelhead in the Keogh River have declined by an order of magnitude because of a period of poor smolt-to-adult survival. Low abundance has been associated with more depressed production of out-migrating smolts than would be expected based on traditional models of compensatory dynamics. Patterns of juvenile density over time show changes in the spatial distribution of the population. We developed a spatially explicit population model to explore spatial structure and juvenile recruitment under varying marine survival. Results suggest that spatial contraction during a period of poor marine survival can strengthen density-dependent population regulation, reducing smolt production at the watershed scale. Our results highlight that spatial contraction can alter the fundamental density-dependent relationships that define population dynamics, recovery trajectories, and sustainable harvest levels of spatially structured populations.

Kerapatan dan Kelulushidupan pada Rekrutmen Karang Pocillopora damicornis (Density and Survivorship on the Recruitment of the brooding coral Pocillopora damicornis)

Studi rekrutmen karang Pocillopora damicornis telah dilakukan dengan mengamati kerapatan juvenil pada substrat penempelan di dataran terumbu Pulau Panjang, Jepara, Jawa Tengah. Hasil menunjukkan bahwa rekrutmen terjadi sepanjang tahun dan tertinggi pada periode Agustus-Oktober. Laju rekrutmen karang di belakang terumbu (back reef) pada sisi bawah angin (selatan) lebih tinggi daripada di sisi atas angin (utara) Pulau Panjang, tampaknya hal ini berkorelasi dengan kerapatan populasi karang dewasanya. Kerapatan juvenil karang tertinggi pada substrat batu alam terjadi pada sisi bawah permukaan substrat, akan tetapi pertumbuhan juvenil karang tertinggi ditemukan di sisi atas permukaan substrat. Hal ini mengindikasikan bahwa kerapatan juvenil karang berhubungan dengan kelulusan hidup juvenil karang. Semakin tinggi kerapatan juvenil karang P. damicornis maka semakin rendah kelulusan hidup juvenil karang karena terjadinya peningkatan persaingan sesama juvenil karang dan akibat kekurangan cahaya. Kata kunci: rekrutmen, kerapatan, kelulushidupan, karang Pocillopora damicornis Recruitment of the brooding coral Pocillopora damicornis was studied by observing the juvenile density on the settlement plate substrate in reef flat of Panjang Island, Jepara, Central Java. The results show that recruitment occurs throughout the year and the highest in the period from August to October. The rate of recruitment of coral reefs in back reef on the leeward (south) is higher than on the windward (north) of the island, it seems to be correlated with population density of adult corals. The highest density of juvenile corals on natural substrata occurs on the lower side surface of the substrate, but the highest growth of juvenile are found on the upper side surface of the substrate. This indicates that the density of juvenile corals associated with the survival of juvenile corals. The higher density of juvenile corals P. damicornis, the lower the survival of juvenile corals due to an increase in competition among juvenile corals and due to lack of light. Keywords: recruitment, density, survivorship, coral Pocillopora damicornis