DOI: 10.17026/dans-z5u-b964
title: Data from: Settlement, seasonal size distribution and growth of the invasive bivalve Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae) in relation to environmental factors.

description: Data from: Settlement, seasonal size distribution and growth of the invasive bivalve Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae) in relation to environmental factorsJournal of Shellfish Research 36(2): 417-426Marinus van der Gaag, Gerard van der Velde and Rob S.E.W. LeuvenIntroductionWith the data in this archive, we share the data from the study of settlement, seasonal size distribution and growth of Mytilopsis leucophaeata in relation with environmental factors. This is a part of the study of the invasive mussel, M. leucophaeata, performed in the North Sea canal in Velsen near the jetty of the ferry landing site, to obtain more insight in its autecology and life history, which is the aim of the thesis.Experimental set-up for the studySampling of water quality parametersPhysico-chemical properties of the surface water of the canal were measured monthly, viz. water temperature (0C) with a mercury thermometer , salinity with an YSI model 33 S-C-T meter. At each date a water sample was taken for measuring chlorophyll a (µg.l-1) at the laboratory.Collecting mussels from the stonesTwo to five stones were collected monthly from the littoral zone of the North Sea canal near the ferry landing site of Velsen at depths of 40-80 cm in the period 1989-1992. Care was taken that sufficient mussels attached to stones were collected, allowing population structure analysis based on shell length-frequency distributions. All stones were transported to the laboratory. Subsequently, all mussels were removed, counted and their shell lengths were measured using a Verniers caliper with an accuracy of 0.05 mm. The stones were measured on all colonized sides to enable sampled surface area calculations.Sampling of Mussels from PVC PanelsPolyvinylchloride (PVC) panels (32.0 x 14.2 x 0.2 cm) were used to study the settlement of spat, density and growth of the mussels. The panels were stuck directly into PVC tubes (length 71.0 cm, inside diameter 14.3 cm). The PVC tubes were used to protect the panels against water turbulence, waves by passing ships and storms that may have caused damage through scouring by the stones. Crabs and fish could freely enter the tubes so predation was not prevented. Both sides of the panels within the tube could be colonized (total surface area: 900 cm2). The panels were dropped at the stony bottom, at a depth of about 75 cm, and were fixed with stainless steel cables to the jetty near the ferry landing site. Subsequently, once a month one short term exposed panel (one month exposed) and one long-term exposed panel (exposed from February 1989 till the month of sampling) were collected. This experiment lasted from February 22 1989 till August 23 1990. A second series of 14 clean tubes with the same design were dropped at April 5 1990. This experiment lasted until August 28 1991. At the end of each sampling event, the harvested panels were substituted by new ones.The spat and the mussels from the panels, were counted and their shell length was measured. Depending on the density of mussels and spat, 48 to 900 cm2 of the panel area was inspected. If high densities of mussels were observed, three areas of 16 cm2 were inspected (front, middle and rear of the side with the highest density). When the density was low, the entire panel was inspected (900 cm2). The shell length along the anterior-posterior axis of each mussel was measured to an accuracy of 0.05 mm. Densities of spat and mussels were expressed as numbers per square metre. The short-term exposed panels were used to determine the period of spat fall (Van der Gaag et al. 2014). The long-term panels were used to study growth, shell length-frequency distribution and densities of the mussel population after settlement.Age Determination of Mussels in CagesTwo perforated stainless steel cages (40 by 40 cm, height 15 cm, mesh size 2 mm) (all mesh 30 % of the surface), made heavier by a tile at the bottom, with nine perforated compartments measuring 13 x 13 cm were each filled with 280 individuals (35 individuals per compartment). They were dropped on August 18 1992 at the sampling site in the North Sea canal at a depth of about 75 cm. Every month the mussels in these cages were checked and dead mussels removed. After cleaning the cages and returning the living mussels, the cages were dropped back in the canal. These results were used to determine the maximum age of these mussels.Here we described the archived files:2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Fauna_from_Panels.odtCollected animals from the panels from the tubes in the North Sea canal in the period 1989-1991Date = collection date of the panal in MMDDYYno = panel number with area number 1, 2, 3 (outside inside)Area = Collected area of the panel for Mytilopsis leucophaeata and Amphibalanus improvisus, unless 150(90) cm2 = Mytilopsis leucophaeata(Amphibalanus improvisus). Rhithropanopeus harrisii and Potamopyrgus antipodarum always full panel, both sides (= 900 cm2)Mytil. = number of Mytilopsis leucophaeataRhithro. = number of Rhithropanopeus harrisiiPotamap. = number of Potamopyrgus antipodarumBalanus = number of Amphibalanus improvisusMytil./m2 = calculated number of Mytilopsis leucophaeata per square meterJuv = juveniles2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Mytilopsis_cage_experimenten.odtSurvival data collected from the cages posted on the stony bottom at Velsen in the North Sea canal, near the small bridge at the ferry landing stage.Date in DDMMYYNumbers for 2mm size classisExp. = experiment%death = percentage died mussel in the preceding month2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Mytilopsis_data.odtMytilopsis leucophaeata data collected from the stones on the stony bottom, in the North Sea canal, at Velsen, round the small bridge at the ferry landing stage in the period 1989-1992.date = MMDDYYl = shell length in mmh = shell height in mm2021_VanderGaag_Thesis_Mytilopsis_Chapter5_NorthSeaCanal89_94.odtData collected at Velsen in the North Sea canal at the jetty near the ferry at the north side in the period 1989-1994, and in summer 1994 at the power plant Hemweg in Amsterdam and the UNA power plant in Velsenµg/l = microgram per literµS/cm = microSiemens/cmDate in DDMMYY2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Panels_Mytilopsis_data.odtMytilopsis leucophaeata collected from panels in the North Sea canal, at the jetty near the ferry in Velsen in the period 1989-1994.If @ only longer than 50 (shell length in 0.1mm) are measured;If * special part is measured.Panel no = no panel + 1, 2, 3 addition for part of the panel from outside to inside (4cm x 4cm) the tube or the complete panel if no addition (900cm2, both sides of the panel)Date in MMDDYYLength measurement in 0.1 mm (shell length)2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Panels_out_.odtBal = Amphibalanus improvisus, Bal+ = dead animals2021_VanderGaag_Thesis_Mytilopsis_Chapter5_Panels_out_1993.odtPanels collected in april 1993 from the North Sea canal near the ferry in Velsen.Bal = Amphibalanus improvisusDate out: in MMYY