Long-term annual and monthly changes in mysids and caridean decapods in a macrotidal estuarine environment in relation to climate change and pollution

© 2018 Elsevier B.V. A 26-year time series of monthly samples from the water intake of a power station has been used to analyse the trends exhibited by number of species, total abundance, and composition of the mysids and caridean decapods in the inner Bristol Channel. During this period, annual water temperatures, salinities and the North Atlantic Oscillation Index (NAOI) in winter did not change significantly, whereas annual NAOI declined. Annual mean monthly values for the number of species and total abundance both increased over the 26 years, but these changes were not correlated with any of the measured physico-chemical/climatic factors. As previous studies demonstrated that, during a similar period, metal concentrations in the Severn Estuary and Bristol Channel (into which that estuary discharges) declined and water quality increased, it is proposed that the above changes are due to an improved environment. The fauna was dominated by the mysids Mesopodopsis slabberi and Schistomysis spiritus, which collectively contributed 94% to total abundance. Both species, which were represented by juveniles, males, non-brooding females and brooding females, underwent statistically-indistinguishable patterns of change in abundance over the 26 years. When analysis was based on the abundances of the various species, the overall species composition differed significantly among years and changed serially with year. When abundances were converted to percentage compositions, this pattern of seriation broke down, demonstrating that changes in abundance and not percentage composition were responsible for the seriation. As with the number and abundance of species, changes in composition over the 26 years were not related to any of the physico-chemical/climatic factors tested. Species composition changed monthly in a pronounced cyclical manner throughout the year, due to statistically different time-staggered changes in the abundance of each species. This cyclicity was related most strongly to salinity

Baseline survey of the fish fauna of a highly eutrophic estuary and evidence for its colonisation by Goldfish (Carassius auratus)

Abstract This study represents the first quantitative survey of the fish fauna of the highly eutrophic Vasse and Wonnerup estuaries, part of the Ramsar-listed Vasse-Wonnerup Wetland System in south-western Australia. Sampling at five sites in each of these estuaries occurred in January 2012 (austral summer) to provide a species inventory and determine whether the number of species, total density and fish community composition differed between the two water bodies. A total of 18,148 fish were recorded, representing six species across four families. Three species that can complete their life cycle within estuaries, i.e. the atherinids Lepthatherina wallacei and Atherinosoma elongata and the gobiid Pseudogobius olorum, dominated the fish fauna, accounting for >99% of all fish collected. No significant inter-estuary differences were observed in the mean number of species, mean total density or fish community composition. Although the fish community was depauperate in terms of the number of species, total density was high, reflecting the presence of permanent and seasonal barriers to the immigration of marine species into these estuaries and the highly productive nature of this system, respectively. Two introduced freshwater species, i.e. the Eastern Gambusia Gambusia holbrooki and the Goldfish, Carassius auratus, were recorded in the Vasse Estuary. As C. auratus was found in mesohaline conditions, individuals may be able to use the estuary as a ‘saltbridge’ to gain access to other tributaries and/or the Wonnerup Estuary, and thus expand their distribution. These findings are of concern given the potential deleterious biological and ecological effects of these alien species

Differences in Recreational Fishers’ Motivations for Utilising Two Estuarine Fisheries

Effective fisheries management requires an understanding of human dimensions. This study elicited the salient motivations for recreational blue swimmer crab and black bream fishing in Western Australia and whether these views differed depending on the fishing location and/or the characteristics of the fisher. Crab fishers were strongly consumption-orientated and aimed to “catch big crabs” and “catch enough crabs to eat”. Furthermore, 91% consumed their catch, with only 2% practicing catch-and-release fishing. In contrast, 81% of black bream fishers did so for the sport/challenge, with the strongest motivation being to catch a bream considerably above legal size and with food only selected by 15% of respondents; most fishers released caught fish. The marked differences between the fisheries for the two species, which co-occur in the same estuaries, are likely driven by the accessible nature of the crab fishery, ease of catching crabs, the low cost of fishing equipment, and their taste. Fishing for black bream, however, requires more expensive equipment, patience, and a greater skill level. Fishers considered crabbing to be as important as other fishing and outdoor activities, whereas bream fishers considered bream fishing considerably more important, reflecting the trophy nature of this fishery

Selecting from the Fisheries Managers’ Tool-Box: Recreational Fishers’ Views of Stock Enhancement and Other Management Options

As recreational fishers act relatively autonomously, management relies heavily on voluntary compliance. Therefore, understanding fishers’ views on management options can be beneficial. This study used a two-phase approach of face-to-face interviews and subsequent online questionnaires to evaluate recreational fishers’ salient views on issues affecting the Blue Swimmer Crab (Portunus armatus) and Black Bream (Acanthopagrus butcheri) fisheries in Western Australia as well as current and potential management arrangements, including stock enhancement. The strength and heterogeneity of views were also determined. Minimum size limits were mainly considered acceptable or very acceptable, with restricting recreational fishing and spatial closures the least supported management options for both species, in addition to maximum size limits for crabs. These views were not always consistent across fishing locations for each species and among types of crab fishers, indicating heterogeneity in views. Stocking was the most acceptable of the management measures not already utilised for crabs and among the most popular for bream fisheries. Recreational fishers of both species believed stock enhancement could have strong positive outcomes for the abundance of their target species and increase their subsequent catches. They also recognized that some negative outcomes, e.g., increased fishing pressure and environmental issues, might occur but considered them unlikely

Quantifying the Potential Water Filtration Capacity of a Constructed Shellfish Reef in a Temperate Hypereutrophic Estuary

Shellfish reefs have been lost from bays and estuaries globally, including in the Swan-Canning Estuary in Western Australia. As part of a national program to restore the ecosystem services that such reefs once provided and return this habitat from near extinction, the mussel Mytilus galloprovincialis was selected for a large-scale shellfish reef construction project in this estuary. To assess the potential filtration capacity of the reef, estuary seston quality, mussel feeding behavior, and valve gape activity were quantified in the laboratory and field during winter and summer. In general, estuary water contained high total particulate concentrations (7.9–8.7 mg L−1). Standard clearance rates were greater in winter (1.9 L h−1; 17 °C) than in summer (1.3 L h−1; 25 °C), the latter producing extremely low absorption efficiencies (37%). Mussel valves remained open ~97% and ~50% of the time in winter and summer, respectively. They often displayed erratic behavior in summer, possibly due to elevated temperatures and the toxic microalgae Alexandrium spp. Despite numerous stressors, the reef, at capacity, was estimated to filter 35% of the total volume of the estuary over winter, incorporating 42.7 t of organic matter into mussel tissue. The reefs would thus make a substantial contribution to improving estuary water quality

Figure 14. Metapenaeus dalli Post larvae I in Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

Figure 14. Metapenaeus dalli Post larvae I (a) lateral view; (b) first antenna; (c) second antenna; (d) mandible; (e) first maxilla; (f) second maxilla; (g) first maxilliped; (h) second maxilliped; (i) third maxilliped; (j) third pereiopod; (k) fifth pereiopod; (l) pleopods; (m) telson and uropods. Scale bars: a–c, g–m = 0.1 mm; d–f = 0.05 mm.Published as part of Crisp, Jason A., Tweedley, James R., D, Frances M. L., Souza, Partridge, Gavin J. & Moheimani, Navid R., 2016, Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory, pp. 1699-1724 in Journal of Natural History 50 on page 1719, DOI: 10.1080/00222933.2016.1155669, http://zenodo.org/record/399214

Effects of temperature and salinity on larval survival and development of the western school prawn Metapenaeus dalli

Abstract The effects of temperature and salinity on the survival and development of larval Metapenaeus dalli were investigated in two experiments. First, the effects of four temperatures of 22.6, 25.8, 29.4 and 32.6 °C on survival and development time were examined from the Nauplius VI to the Mysis I sub-stage. Survival was significantly lower at 32.6 °C than at 22.6 and 25.8 °C. Development times differed significantly across all temperatures, decreasing linearly with temperature from 161.5 h at 22.6 °C to 74.8 h at 29.4 °C then decreased slightly to 71.4 h at 32.6 °C. Second, the combined effects of three temperatures (21.4, 26.5 and 29.7 °C) and three salinities (30, 35 and 40‰) on survival and development were quantified over a 48 h period from the Nauplius VI sub-stage. Only salinity was found to influence survival, with peak survival (77.7%) found to occur at the control salinity (~35‰). Any increase or decrease in salinity from this value resulted in a decrease in survival, with the lowest salinity tested (30‰) having a significantly negative effect on survival (58.4%) when compared to the control. Only temperature was found to influence the rate of development, with significant increases in development index values being recorded as temperature increased. The recommended conditions for optimal survival and development of M. dalli larvae as determined by this study are, therefore, 25.8 °C and 35‰

Figure 11. Metapenaeus dalli Mysis I in Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

Figure 11. Metapenaeus dalli Mysis I (a) lateral view; (b) first antenna; (c) second antenna; (d) mandible; (e) first maxilla; (f) second maxilla; (g) first maxilliped; (h) second maxilliped; (i) third maxilliped; (j) third pereiopod; (k) fifth pereiopod; (l) telson and uropods. Scale bars: a–c, g– l = 0.1 mm; d–f = 0.05 mm.Published as part of Crisp, Jason A., Tweedley, James R., D, Frances M. L., Souza, Partridge, Gavin J. & Moheimani, Navid R., 2016, Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory, pp. 1699-1724 in Journal of Natural History 50 on page 1714, DOI: 10.1080/00222933.2016.1155669, http://zenodo.org/record/399214

Figure 3. Metapenaeus dalli Nauplius II in Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

Figure 3. Metapenaeus dalli Nauplius II (a) ventral view; (b) first antenna; (c) second antenna; (d) mandible. Scale bar = 0.1 mm.Published as part of Crisp, Jason A., Tweedley, James R., D, Frances M. L., Souza, Partridge, Gavin J. & Moheimani, Navid R., 2016, Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory, pp. 1699-1724 in Journal of Natural History 50 on page 1705, DOI: 10.1080/00222933.2016.1155669, http://zenodo.org/record/399214