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

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

Figure 12. Metapenaeus dalli Mysis II in Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

Figure 12. Metapenaeus dalli Mysis II (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. Abbreviated label (Pt. sp.) is pterygostomain spine. 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 1715, DOI: 10.1080/00222933.2016.1155669, http://zenodo.org/record/399214