Latitudinal variation in growth of Crangon crangon (L.): Does counter-gradient growth compensation occur?

Length growth in relation to water temperature was studied for Crangon crangon (L.) from two populations at the northern and southern edges of its distributional range to determine whether counter-gradient growth compensation occurs. In crustaceans, growth rate depends on the time between moulting events (intermoult period) and the size increase at moult (moult increment). In this study, the period between moults was shorter at higher temperature, ranging respectively from about 11 days at 25 °C to 27 days at 10 °C at southern edge, and from 10 to 24 days at the same temperatures at the northern edge. Moult increment showed a large variability, from 1.5 to 2.7 mm with no clear trend with temperature at the northern edge; and decreasing from about 2.7 mm at 10 °C to about 1.5 mm at 25 °C at the southern edge. As a result, the temperature effect on the overall growth rate differed between shrimps from the north and those from the south, suggesting counter-gradient growth compensation. At the northern edge, mean growth increased from about 0.12 mm d^− 1 at 10 °C to about 0.23 mm d^− 1 at 25 °C, while at the southern edge, growth was lower, about 0.08 mm d^− 1 at 10 °C and increased to about 0.16 mm d^− 1 at 25 °C. Maximum observed growth rates of shrimps from the north were also higher and ranged from 0.17 mm d^− 1 at 10 °C to 0.89 mm d^− 1 at 25 °C, while shrimps from the south grew at a maximum of 0.08 to 0.75 mm d^− 1 respectively at 15 and 20 °C. Sex and size differences were also found, with males growing slower than females and at a decreasing growth rate with increasing size. Implications for the brown shrimp's life cycle are discussed.     

Do agonistic behaviours bias baited remote underwater video surveys of fish?

Marine environments require monitoring to determine the effects of impacts such as climate change, coastal development and pollution and also to assess the effectiveness of conservation measures. Marine protected areas (MPAs) are being established globally and require periodic monitoring to determine whether their objectives are being met. Baited underwater video systems are becoming a popular method for monitoring change within protected fish populations, because they are less damaging to habitats than bottom trawling and allow for more statistical powerful comparisons to determine spatial and temporal patterns in the relative abundances, lengths and biomass of demersal and pelagic fishes. However, much remains uncertain about how interactions between the fish and bait and between the fish themselves affect the results obtained. Agonistic behaviours are frequently observed around the bait of the camera and potentially bias fish density estimates by altering the number and size classes seen at cameras. Here we counted the number of agonistic behaviours between pink snappers (Pagrus auratus), the size of fish involved and whether the fish left the field of view following such behaviours. The study consisted of 20 baited underwater video deployments inside a New Zealand marine reserve and 20 in adjacent open areas. We observed a significant relationship between the peak number of fish observed at the camera and the total number of agonistic behaviours, as well as the number of both aggressor and subordinate fish leaving the camera field of view following interactions. The slope of the latter relationship and thus the absolute numbers of fish leaving were higher for subordinate fish. As subordinates were significantly smaller than aggressors, the apparent size frequency distribution is likely skewed away from smaller size classes. The staying time of the fish and thus the maximum number of fish present at the camera will be reduced by agonistic behaviours and the absolute magnitude of this effect appears to be greater at high fish densities. Our results suggest that an overall effect of these phenomena is to underestimate the differences in abundance between MPAs and open areas, but also to overestimate differences in average size.     

Does bivalve mucus favour the growth of their main food source,microalgae?

Bivalves, by releasing inorganic nutrients, can stimulate the growth of the primary producers on which they feed. Dissolved excretion and mineralization of biodeposits (pseudofaeces and faeces), two indirect processes related to their feeding activity, have already been identified. This study investigated whether microalgal growth is also dependent on the mucus secreted by bivalves and rejected with their biodeposits. An experimental study based on algal growth tests was conducted to determine whether the mucus coating the pseudofaeces and faeces of the oyster Crassostrea gigas (Thunberg) could stimulate the growth of nine marine microalgae: a Prasinophyceae [Tetraselmis suecica (Butcher)] and eight Diatomophyceae [Amphora sp. (Ehrenberg), Chaetoceros sp. (Ehrenberg), Entomoneis alata (Ehrenberg), Haslea ostrearia (Simonsen), Nitzschia acicularis (Wm Smith), N. closterium (Wm Smith), N. gandersheimiensis (Krasske) and Skeletonema costatum (Cleve)]. Oysters were fed only inorganic particles at a concentration well above the threshold of pseudofaeces production. A fraction of pseudofaeces and faeces was then inoculated into glass tubes containing a single algal species. Algal growth tests showed that mucus stimulated the growth of four of the nine species studied: Chaetoceros sp., H. ostrearia, N. gandersheimiensis and T. suecica. The strongest responses were observed with H. ostrearia and Chaetoceros sp., for which mean algal biomass was significantly higher with mucus originating from pseudofaeces than faeces. Monitoring of the release of dissolved components from mucus showed significant enrichment in inorganic phosporus. The use of an antibiotic treatment suggested that this dissolved component is released by simple solubilization rather than by bacterial breakdown.     

Do marine protected areas deliver flows of ecosystem services to support human welfare?

This paper examines the potential relationships between the ecosystem services provided by the coastal and marine environment and the designation of marine protected areas. The hypothesis is that relationships exist between the provision of ecosystem services and the features protected by marine protected areas. It is considered that protection will maintain these features in good ecological condition and in some cases will restore ecological functioning with positive effects on the delivery of ecosystem services, as pressures upon the protected features are reduced. As the number of marine protected area designations grows, system-wide effects to communities from improvements in delivery of a range of ecosystem services may be realised. This paper provides a comparative analysis of the jurisdictional marine protected area policies proposed by the English, Welsh and Scottish Governments. It presents structured assessment matrices developed from the literature and expert opinion, of ecosystem service provision by marine protected habitats and species and applies the findings to a range of existing UK marine protected areas to demonstrate its relevance. The approach and case study findings are discussed within the wider context of marine ecosystem services and marine protected area management.     

Phosphate limitation of phytoplankton growth in the Changjiang Estuary

Laboratory experiments of bioassay with Pltaeodaetytum tricornutum, Chatoceros didymus, Chaetoreros calcitraus and Heterogtoea sp. sampled from the Changjiang Estuary in spring and summer, 1986, indicated that both N and P limit phytoplankton growth in the medium with N : P ranged between 8-30, and N limits phytoplankton production in the medium with N: P<8, while P is the limitary nutrient in the N : P>30. Generally, N : P in the Changjiang Estuary waters is 2 times higher than Redfield ratio. The bioassay experiments with high N : P water samples collected from Changjiang Estuary show that phytoplankton production is limited by P. Phytopiankton appears to give priority to the uptake of P at all periods of time. And the optimum N:P for phytoplankton growth is determined to be 18.     

Notes Effects of four nitrogen substrates on growth of several red tide species

Eight common red tide species including the Dinoflagellates Alexcandrium tamarense,Prorocentrum minimum , Prorocentrum mican , Diatoms Skeletonema costatum , Cerataulina pelag-ica, Leptocylindrus minimus, a Raphidophyte Heterosigma akashiwo and a Chrysophyte Isochrysis galbana were chosen to study the effect of four nitrogen substrates (NO_3 - N, NH_4 - N, Urea - N, Mixed - N) on the growth of these algae. After two transfers, the results showed that at N concentration of 550 μmol,, NO_3 - N was the best nitrogen source among these four nitrogen substrates; Urea - N and Mixed - N were also good for the growth of most algae, but not as good as NO_3 - N for some species; NH_4 - N inhibited the growth of all these species except H. akashiwo. At concentrations of 280 and 50 μmol experiments on the growth of I. galbana , P. minimum and L. minimus in NH_4 - N and NO_3 - N substrates were also performed. The results showed that the growth rates of I. galbana were not significantly different from each other in     

Do environmental factors influence the movement of estuarine fish? A case study using acoustic telemetry

Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitters and manually tracked during two periods (7 February to 24 March 2003; n = 20 and 29 September to 15 November 2003; n = 20). Real-time data revealed that spotted grunter are euryhaline (0–37) and are able to tolerate large variations in turbidity (4–356 FTU) and temperature (16–30 °C). However, the fish altered their position in response to large fluctuations in salinity, temperature and turbidity, which are characteristic of tidal estuarine environments. Furthermore, tidal phase had a strong influence on the position of spotted grunter in the estuary.     

Exploitation and conservation of coastal and marine fisheries in Bangladesh: Do the fishery laws matter?

The present study analysed the major features of two important acts and an ordinance in Bangladesh that govern coastal and marine fishery exploitation and conservation. The problems with the implementation of these regulations were identified, and the level of compliance among fishers and reasons for their noncompliance were assessed. Based on two case studies on coastal and marine ecosystems, the findings revealed that the level of noncompliance is highly prevalent, particularly in hilsa sanctuaries in the Meghna River estuary. The study identified coastal poverty, the inadequate and improper distribution of incentives, insufficient logistic support, limited alternative occupations, political interference and a lack of awareness regarding fishery regulations as the major limitations in the implementation. The drawbacks of proper implementation and the noncompliance of fishery regulations lead to fishery degradation, directly affect the sustainability of the coastal and marine ecosystem of Bangladesh and may be barriers to achieving Goal 14 of the Sustainable Development Goals (SDGs). Establishing a co-management mechanism for sanctuary management, creating economic opportunities outside of fishery sectors, declaring more protected areas in the coastal and marine ecosystem, enhancing logistic support to the enforcing agencies and building awareness are critical to improving the compliance level among fishers. Finally, the study submits that understanding the fishers’ reasons for compliance and noncompliance of the regulations is important for devising fishery policies through the consultation and engagement of stakeholders at all levels.     

Influence of water logging time on the growth of Kandelia candel seedlings

Influence of waterlogging time on the growth of Kandelia candel(L.) Druce seedlings grown for 70 d in the artificialtidal tanks‘ simulated semidiurnal tide under greenhouse is studied. Sand and soil act as the substrate and artificial seawater with salinity of 15 is used in cultivation. Shorter waterlogging time (inundated for about 2 ～ 4 h) promotes the growth of K candel seedlings, while longer time (inundated more than 8 h) or no waterlogging (0 h) inhibits their growth. The number and length of aerating roots increase with the increase of waterlogging time. Under existing conditions, the optimal waterlogging time for the growth of K. candel seedlings is about 2 ～ 4 h in every tide cycle. Compared with other treatments, the 2 h sanded treatments obtain the highest biomass of seedlings, have the lowest mass loss ofhypocotyl and broaden the photosynthetic area by increasing the area per leaf after 70-d cultivation. And the soil treatments have the similar tendency. However, waterlogging for 8h in every tide cycle is critical for normal development of seedlings.K. candel seedlings are highly tolerant to waterlogging and a proper waterlogging is beneficial to the growth of K. candel seedlings.     

A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030

Ocean noise levels are thought to be increasing as a result of major growth in global shipping activity, but data quantifying those changes are limited in space and time. As an alternative approach, this study examines the current and future maximum noise capacity of three segments of the global commercial shipping fleet: container ships, oil tankers, and bulk carriers. It shows that continued growth in the number of ships, the quantity of goods carried and the distances traveled could increase the maximum noise capacity of the global shipping fleet by up to a factor of 1.9 by 2030, with major growth in particular in the container and bulk carrier segments. Thus, in the absence of operational or manufacturing changes to such ships, the contribution of commercial shipping to ambient ocean noise levels can be expected to dramatically increase.     

Do predatory fish of benthic crustaceans vary between kelp and barren reef habitats in northeastern New Zealand?

Fish assemblages that included known predators of benthic crustaceans were compared between kelp and barren habitats in northeastern New Zealand using baited underwater video census methods. The benthic-feeding fish were observed in winter, spring/summer and autumn, as well as during night-time in spring/summer. Overall, the fish assemblages varied between barren and kelp habitat, being most marked in winter. Individual benthic-feeding species, such as grey mao mao (Scorpis lineolatus) and leatherjacket (Meuschenia scaber) were associated with barren habitat, while the spotted wrasse (Notolabrus celidotus) was more strongly associated with kelp habitat. The results suggest that changes in habitats on coastal reefs affect populations of species that are benthic predators, which may in turn influence the distribution and abundance of their prey species, such as juvenile spiny lobsters.     

Do the shallow‐water habitats of a hypersaline tropical estuary act as nursery grounds for fishes?

Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern were salinity and depth, which were related to spatial segregation. Species richness was lowest in the upper zone, an area with high salinity and shallow depth. The distinct roles of structurally different habitats (submerged macrophyte beds and mangrove prop‐roots) and the influence of physicochemical conditions in the middle zone of the estuary may influence taxonomic diversity. The middle zone of the estuary is the one most attractive to juveniles of reef species (Lutjanidae and Serranidae). The fish assemblages are clearly dominated by marine estuarine dependent species, highlighting the importance of the ecosystem as a nursery ground for marine species of the Brazilian coast.     

Effects of β-ecdysone and polypodine-B on moulting and growth of prawn, Penaeus orientalis

Effects of the mixture of β-ecdysone and polypodine -B (2 : 1 W/W) on the moulting and growth of prawn, Penaeus orientaliss were studied in laboratory by rearing the animal with the added compound diets. The results showed that the addition of the moulting hormone (M. H) mixture to compound diets, from 1. 33× 10-6 to 30×10-6, could increase moulting activity and growth rate of the prawn to different extents, among which the 5. 33× 10-6-10. 67×10-6addition had statistically significant effects. However, 60 × 10-6 added diets caused moulting and growth inhibitions and cuticle thickening. The analyses of protein, water and ash contents of the prawn showed no remarkable differences between hormone dosed animals and the control.     

Relationship between somatic growth and otolith growth: a case study of the ornate jobfish Pristipomoides argyrogrammicus from the coast of Réunion (SW Indian Ocean)

The ornate jobfish Pristipomoides argyrogrammicus Valenciennes 1832 occurs in the Indo-West Pacific Ocean, where it is harvested by small-scale coastal fisheries. Management of this species is hindered by lack of adequate biological data. We sampled a total of 113 individuals from the landings of local artisanal fishers on the island of Réunion (southwestern Indian Ocean), from March 2014 to March 2015. The relationships between two types of body length (total and standard length, cm) and total weight (g) were shown to be significant (p < 0.05). The length–weight relationship was described by a power function, with the scaling factor estimated to be 0.008 and the exponent 3.146. Age was determined using whole otoliths. The von Bertalanffy growth equation was estimated to be TL_t = 30.68(1 – e^?0.52(t)). Otolith morphometry variables (length, width and area) were significantly correlated with age estimates (p < 0.05). No significant difference in age estimates was observed between left and right otoliths used as predictors. Readings from observed age and the estimates from modelled age indicated relatively good agreement, suggesting the potential to use whole otoliths for age estimation.     

Vertical distribution and growth performance of Baltic cod larvae – Field evidence for starvation-induced recruitment regulation during the larval stage?

Besides variable egg survival, previous studies suggested that the larval stage may be the most critical phase in determining Baltic cod recruitment variability, and that larvae need to conduct an ontogenetic vertical migration from hatching depths (>50 m) to upper layers with increased food availability in order to initiate first feeding, improve their nutritional condition and growth, and avoid starvation. Recently, detailed information on the stage-resolved vertical distribution of main Baltic copepod species, including the preferred larval Baltic cod prey species Pseudocalanus acuspes, has become available. Therefore, the vertical distribution of Baltic cod larvae in August 2007 and their depth-dependent nutritional condition and growth were investigated. RNA–DNA based methods were used to estimate growth, including a novel approach to estimate growth performance by relating observed specific growth rates (SGR) of field caught larvae to temperature-dependent reference growth rates (G_ref) for fast-growing laboratory reared fish from the literature. This standardization to G_ref was found to have a great potential to improve investigations on the growth and ecology of larval fish. The need for early larvae to migrate to shallower layers was corroborated, while larger size classes were found at increasingly greater depths. This may reflect a continuation of the ontogenetic vertical migration in order to follow increasingly larger prey items at greater depths and to save energy in cooler waters below the thermocline. Larval growth generally declined with increasing depth, but the decline in growth became less pronounced in larger size classes. This indicates that larger larvae were better in coping with the ambient environment and the available prey field at greater depths. Generally, Baltic cod larvae grew poorly compared to larvae from other studies, which is discussed in relation to differences in predation and a possible food–temperature trade-off for larvae in the highly stratified Baltic Sea. Comparison with earlier results showed a higher frequency of starving larvae and lower frequencies of larger larvae after the first-feeding stage in 1994 and 1995. As this was a period of low Baltic cod recruitment despite favourable conditions for egg survival, it is concluded that larval starvation mortality has a high potential to contribute to recruitment variability in Baltic cod.     

Effects of salinity fluctuation in different ranges on the intermolt period and growth of juvenile Fenneropenaeus chinensis

1 Introduction Salinity is an important environmental parameter affecting the growth of the crustaceans, and the toler- ance to salinity varies with species and growth periods. Marsupenaeus japonicus is sensitive to salinity fluctua- tion, and abrupt decrease in salinity can result in high mortality (Chen and Bian, 1994). As reported by Dall (1981), tolerance of the juvenile Metapenaeus bennet- tae, Penaeus esculentus and Fenneropenaeus mer- guiensis to salinity fluctuation is not as strong …