Implementation<\/h2>\r\nAt the first Ecosim and Ecospace time steps, a base scalar is calculated:\r\n\r\n[latex]a_i = NAge1_i \/ NAge1_j\\tag{1}[\/latex]\r\n
where \ud835\udc4e is the scalar, i<\/em> is a multi\u2010stanza group whose recruitment is driven by multi\u2010stanza group j<\/em>, and NAge1<\/em> is the number of individuals at age 1, e.g., the number of recruits, for multi\u2010stanza groups i<\/em> and j<\/em>. This base scalar serves to maintain the ratio between the number of gender\u2010split recruits during the simulations.<\/p>\r\n For every consecutive time step, the number of multi\u2010stanza group i<\/em> recruits is then set as follows:<\/p>\r\n[latex]NAge1_i = a_i x NAge1_j\\tag{2}[\/latex]\r\n Changes to the EwE computations were minimal; the most challenging code changes were made in the Ecospace IBM model [footnote]Walters, C., Christensen, V., Walters, W., Rose, K., 2010. Representation of multistanza life histories in Ecospace models for spatial organization of ecosystem trophic interaction patterns. Bulletin of Marine Science<\/a> 86, 439\u2013459.[\/footnote], where parallel computations was reorganized to ensure that multi\u2010stanza recruitment is calculated in the correct order. Ecospace does not yet calculate recruitment success from spatial overlap of the gender\u2010split stanza; this could be a future refinement if needed.<\/p>\r\n An example of the impact of linked recruitment is shown in Figure 1. Here, Ecosim is executed for a model that contains separate multi\u2010stanza groups for male and female snow crab Chionoecetes opilio<\/em>. Both multi\u2010stanza groups consist of two life stages each: juveniles and adults. Only the male snow crabs are fished. The model contains no change in environment and fishing other than gradually intensifying effort of the snow crab fishery. Figure 1 shows three simulations: in the left panel, multi\u2010stanza recruitment is not linked. In the middle panel, female recruitment is obtained from the male multi\u2010stanza group. In the right panel, male recruitment is obtained from the female multi\u2010stanza group.<\/p>\r\n \r\n\r\n[caption id=\"attachment_752\" align=\"aligncenter\" width=\"949\"] First, define the male and female multi\u2010stanza configurations in the Define groups<\/em> interface (Figure 4).<\/p>\r\n \r\n\r\n[caption id=\"attachment_753\" align=\"aligncenter\" width=\"739\"] Second, configure the two gender\u2010split multi\u2010stanza groups in the \u201cEdit multi\u2010stanza\u201d interface (not shown here).<\/p>\r\n Third, link recruitment in the \u201cEdit multi\u2010stanza\u201d interface. In the figure below, female snow crab recruitment is linked to the males. A multi\u2010stanza group whose recruitment is linked will have its recruitment calculations overwritten, and therefore the \u201cRecruitment Power\u201d parameter becomes inactive (Figure 5).<\/p>\r\n \r\n\r\n[caption id=\"attachment_754\" align=\"aligncenter\" width=\"760\"] Occasionally, ecosystem modellers run into issues where gender\u2010split populations need explicit modelling. This can occur when empirical data is only available for male or female specimens, or when males and females of key species have markedly different behaviours. We have made a small modification to the Ecopath with Ecosim (EwE) multi\u2010stanza model [1]<\/sup><\/a>, that allows linking recruitment to ensure proportional spawning between two multi\u2010stanza groups, and thus connecting two gender\u2010spilt populations at their foundation.<\/p>\n At the first Ecosim and Ecospace time steps, a base scalar is calculated:<\/p>\n [latex]a_i = NAge1_i \/ NAge1_j\\tag{1}[\/latex]<\/p>\n where \ud835\udc4e is the scalar, i<\/em> is a multi\u2010stanza group whose recruitment is driven by multi\u2010stanza group j<\/em>, and NAge1<\/em> is the number of individuals at age 1, e.g., the number of recruits, for multi\u2010stanza groups i<\/em> and j<\/em>. This base scalar serves to maintain the ratio between the number of gender\u2010split recruits during the simulations.<\/p>\n For every consecutive time step, the number of multi\u2010stanza group i<\/em> recruits is then set as follows:<\/p>\n [latex]NAge1_i = a_i x NAge1_j\\tag{2}[\/latex]<\/p>\n Changes to the EwE computations were minimal; the most challenging code changes were made in the Ecospace IBM model [2]<\/sup><\/a>, where parallel computations was reorganized to ensure that multi\u2010stanza recruitment is calculated in the correct order. Ecospace does not yet calculate recruitment success from spatial overlap of the gender\u2010split stanza; this could be a future refinement if needed.<\/p>\n An example of the impact of linked recruitment is shown in Figure 1. Here, Ecosim is executed for a model that contains separate multi\u2010stanza groups for male and female snow crab Chionoecetes opilio<\/em>. Both multi\u2010stanza groups consist of two life stages each: juveniles and adults. Only the male snow crabs are fished. The model contains no change in environment and fishing other than gradually intensifying effort of the snow crab fishery. Figure 1 shows three simulations: in the left panel, multi\u2010stanza recruitment is not linked. In the middle panel, female recruitment is obtained from the male multi\u2010stanza group. In the right panel, male recruitment is obtained from the female multi\u2010stanza group.<\/p>\n <\/p>\n First, define the male and female multi\u2010stanza configurations in the Define groups<\/em> interface (Figure 4).<\/p>\n <\/p>\n Second, configure the two gender\u2010split multi\u2010stanza groups in the \u201cEdit multi\u2010stanza\u201d interface (not shown here).<\/p>\n Third, link recruitment in the \u201cEdit multi\u2010stanza\u201d interface. In the figure below, female snow crab recruitment is linked to the males. A multi\u2010stanza group whose recruitment is linked will have its recruitment calculations overwritten, and therefore the \u201cRecruitment Power\u201d parameter becomes inactive (Figure 5).<\/p>\n <\/p>\n Linked stanza recruitment was implemented by Jeroen Steenbeek after an idea by Villy Christensen under project EISA: Ecology and management of the invasive snow crab<\/em><\/a>.<\/p>\n![\"\"](\"https:\/\/pressbooks.bccampus.ca\/eweguide\/wp-content\/uploads\/sites\/2056\/2023\/10\/Picture1.png\")
Figure 1<\/b> \u2010 Three Ecosim simulations with different recruitment linkage configurations for snow crab: no linked recruitment (Left), female recruitment linked to the fished males (Center), and fished male recruitment linked to non\u2010fished females (Right). Note that both juvenile groups are identically parameterized in this specific case, and therefore their biomass estimates exactly overlap in the Center and Right plots.[\/caption]\r\nConfiguring Linked Stanza Recruitment<\/h2>\r\n
![\"\"](\"https:\/\/pressbooks.bccampus.ca\/eweguide\/wp-content\/uploads\/sites\/2056\/2023\/10\/Picture2.png\")
Figure 2<\/b> \u2010 Define gender\u2010split multi\u2010stanza groups[\/caption]\r\n![\"\"](\"https:\/\/pressbooks.bccampus.ca\/eweguide\/wp-content\/uploads\/sites\/2056\/2023\/10\/Picture3.png\")
Figure 3 <\/b>\u2010 Linking the recruitment of a multi\u2010stanza configuration to another multi\u2010stanza.[\/caption]\r\nAttribution<\/h1>\r\nLinked stanza recruitment was implemented by Jeroen Steenbeek after an idea by Villy Christensen under project EISA: Ecology and management of the invasive snow crab<\/em><\/a>.","rendered":"
Background<\/h2>\n
Implementation<\/h2>\n
Configuring Linked Stanza Recruitment<\/h2>\n
Attribution<\/h1>\n