diff --git a/NEWS.md b/NEWS.md
index c423a4e..abe0409 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,6 +1,8 @@
 # 1.5.0-9004
+* Added / exposed function for collapsing strata on IndividualSamplingParameters (CollapseStrata)
 * Added documentation for dealing with incomplete biological records (#170)
 * Made stratification options for ComputePsuSamplingParameters more flexible (#171)
+* Fixed a bug with handling of NA values in AddLengthGroupStoxBiotic
 * Fixed a bug with missing error detection when trying to report estimates over several strata (#173)
 * Fixed a bug which would cause duplicate samplingUnitIds in the SelectionTable when running ComputePsuSamplingParameters with the option "adHocStoxBiotic" (#172)
 * Fixed a bug which cause the menu for ExtendAnalyticalSamplingFrameCoverage to not show options for StratificationVariables
diff --git a/R/StoxAnalyticalBaselineFunctions.R b/R/StoxAnalyticalBaselineFunctions.R
index d6d1708..00596bd 100644
--- a/R/StoxAnalyticalBaselineFunctions.R
+++ b/R/StoxAnalyticalBaselineFunctions.R
@@ -776,9 +776,6 @@ AssignPSUSamplingParameters <- function(PSUSamplingParametersData, StoxBioticDat
 #'  If any strata are specified in the SampleTable of 'IndividualSamplingParametersData' but are not sampled per the SelectionTable
 #'  all estimates will be provided as NAs for this stratum.
 #'  
-#'  Domains that are not present in a sample are not reported, although their estimated abundance and total is zero. Use the function
-#'  \code{\link[RstoxFDA]{LiftStrata}} to infer zero values for unreported domains, and mark unsampled strata as NA.
-#'  
 #'  In general unbiased estimates rely on known inclusion probabilites, and domain definitions that coincides
 #'  with stratification. When the domain definitions are not aligned
 #'  with the stratification, ratio estimates are provided for which unbiasedness is not guaranteed.
@@ -1333,7 +1330,7 @@ AnalyticalPopulationEstimate <- function(PSUSamplingParametersData, AnalyticalPS
   
   NestimatesByStrata <- AnalyticalPSUEstimateData$Abundance[,list(estimates=get(".N")),by="Stratum"]
   if (!length(unique(NestimatesByStrata$estimates))==1){
-    stop("Cannot Estimate with heterogeneous lower level stratification. Consider the functions LiftStrata or CollapseStrata.")
+    stop("Cannot Estimate with heterogeneous lower level stratification. Consider the function CollapseStrata.")
   }
   
   LowerLevelStrata <- AnalyticalPSUEstimateData$StratificationVariables[!duplicated(get("Stratum")),.SD, .SDcol=names(AnalyticalPSUEstimateData$StratificationVariables)[names(AnalyticalPSUEstimateData$StratificationVariables)!="SampleId"]]
@@ -1353,8 +1350,8 @@ AnalyticalPopulationEstimate <- function(PSUSamplingParametersData, AnalyticalPS
   missingMean <- AnalyticalPSUEstimateData$Variables$SampleId[is.na(AnalyticalPSUEstimateData$Variables$Mean) & !is.nan(AnalyticalPSUEstimateData$Variables$Mean)]
   
   if (!MeanOfMeans & (length(missingAbund)>0 | length(missingTotal)>0)){
-    msg <- "Cannot estimate. Estimates are not provided for all samples in 'AnalyticalPSUEstimateData'."
-    if (length(missingFreq)==0 & length(missingMean)==0){
+    msg <- "Cannot estimate. Abundance- or total-estimates are not provided for all samples in 'AnalyticalPSUEstimateData'."
+    if (length(missingFreq)==0 | length(missingMean)==0){
       msg <- paste(msg, "Consider the option MeanOfMeans.")
     }
 
@@ -1364,7 +1361,7 @@ AnalyticalPopulationEstimate <- function(PSUSamplingParametersData, AnalyticalPS
   }
 
   if (MeanOfMeans & (length(missingFreq)>0 | length(missingMean)>0)){
-    msg <- "Cannot estimate. Estimates are not provided for all samples in 'AnalyticalPSUEstimateData'."
+    msg <- "Cannot estimate. Frequency- or means-estimates are not provided for all samples in 'AnalyticalPSUEstimateData'."
     missing <- unique(c(missingFreq, missingMean))
     
     msg <- paste(msg, "Missing for SamplingUnitIds:", truncateStringVector(missing))
@@ -1578,6 +1575,7 @@ AnalyticalRatioEstimate <- function(AnalyticalPopulationEstimateData, StoxLandin
 
   checkMandatory(AnalyticalPopulationEstimateData, "AnalyticalPopulationEstimateData")
   checkMandatory(StoxLandingData, "StoxLandingData")
+  checkLandingsNotEmpty(StoxLandingData)
   checkMandatory(WeightVariable, "WeightVariable")
   checkOptions(Method, "Method", c("TotalDomainWeight", "MeanDomainWeight"))
   checkMandatory(StratificationVariables, "StratificationVariables")
@@ -1958,6 +1956,7 @@ ExtendAnalyticalSamplingFrameCoverage <- function(AnalyticalPopulationEstimateDa
   
   checkMandatory(AnalyticalPopulationEstimateData, "AnalyticalPopulationEstimateData")
   checkMandatory(StoxLandingData, "StoxLandingData")
+  checkLandingsNotEmpty(StoxLandingData)
   checkMandatory(StratificationVariables, "StratificationVariables")
   checkOptions(Method, "Method", c("Strict", "SetToStratum"))
   checkMandatory(UnsampledStratum, "UnsampledStratum")
@@ -2342,6 +2341,7 @@ InterpolateAnalyticalDomainEstimates <- function(AnalyticalPopulationEstimateDat
   
   checkMandatory(AnalyticalPopulationEstimateData, "AnalyticalPopulationEstimateData")
   checkMandatory(StoxLandingData, "StoxLandingData")
+  checkLandingsNotEmpty(StoxLandingData)
   checkOptions(Method, "Method", c("Strict", "StratumMean"))
   if (Method=="StratumMean"){
     checkMandatory(DomainMarginVariables, "DomainMarginVariables")
@@ -2513,8 +2513,8 @@ AddLengthGroupStoxBiotic <- function(StoxBioticData, LengthInterval=numeric(), L
   }
   StoxBioticData$Individual[[LengthGroupVariable]] <- as.character(
     cut(StoxBioticData$Individual$IndividualTotalLength, 
-        seq(0, max(StoxBioticData$Individual$IndividualTotalLength)+LengthInterval, LengthInterval), 
+        seq(0, max(StoxBioticData$Individual$IndividualTotalLength,na.rm=T)+LengthInterval, LengthInterval), 
         right=LeftOpen))
-  
+  StoxBioticData$Individual[[LengthGroupVariable]][is.na(StoxBioticData$Individual$IndividualTotalLength)] <- as.character(NA)
   return(StoxBioticData)
 }
\ No newline at end of file
diff --git a/R/StoxBaselineFunctions.R b/R/StoxBaselineFunctions.R
index dca2126..7abadb7 100644
--- a/R/StoxBaselineFunctions.R
+++ b/R/StoxBaselineFunctions.R
@@ -1,5 +1,13 @@
-
-
+#' Halts with error if StoxLandingData is empty
+#' @noRd
+checkLandingsNotEmpty <- function(StoxLandingData){
+  if (!RstoxData::is.StoxLandingData(StoxLandingData)){
+    stop("Malformed StoxLandingData")
+  }
+  if (nrow(StoxLandingData$Landing)==0){
+    stop("StoxLandingData is empty.")
+  }
+}
 
 #' Checks symmetry of Car table
 #' @noRd
@@ -929,6 +937,7 @@ AddGearGroupStoxLanding <- function(StoxLandingData, Translation){
   
   checkMandatory(StoxLandingData, "StoxLandingData")
   checkMandatory(Translation, "Translation")
+  checkLandingsNotEmpty(StoxLandingData)
   
   if (!is.Translation(Translation)){
     stop("Translation is not a valid Translation table.")
diff --git a/R/StoxDataTypes.R b/R/StoxDataTypes.R
index be529a1..8ee9a55 100644
--- a/R/StoxDataTypes.R
+++ b/R/StoxDataTypes.R
@@ -2456,6 +2456,14 @@ stoxFunctionAttributes <- list(
       )
     )
   ),
+  CollapseStrata = list(
+    functionType = "modelData", 
+    functionCategory = "baseline", 
+    functionOutputDataType = "IndividualSamplingParametersData",
+    functionParameterFormat = list(
+      RetainStrata = "collapsestrataretain"
+    )
+  ),
   ComputePSUSamplingParameters = list(
     functionType = "modelData", 
     functionCategory = "baseline", 
@@ -3384,6 +3392,15 @@ processPropertyFormats <- list(
       return(pv)
     },
     variableTypes = "character"
+  ),
+  collapsestrataretain = list(
+    class = "vector",
+    title = "Strata to retain from collapse", 
+    possibleValues = function(IndividualSamplingParametersData){
+      pv <- unique(IndividualSamplingParametersData$StratificationVariables$Stratum)
+      return(pv)
+    },
+    variableTypes = "character"
   )
 )
 
diff --git a/inst/tinytest/test-StoxAnalyticalBaselineFunctions.R b/inst/tinytest/test-StoxAnalyticalBaselineFunctions.R
index 54d09de..0bb5d37 100644
--- a/inst/tinytest/test-StoxAnalyticalBaselineFunctions.R
+++ b/inst/tinytest/test-StoxAnalyticalBaselineFunctions.R
@@ -273,7 +273,7 @@ stationDesign <- RstoxFDA:::ComputePSUSamplingParameters(StoxBioticData = ss, Sa
 sexStrat <-  RstoxFDA:::ComputeIndividualSamplingParameters(ss, "Stratified", c("IndividualAge"), StratificationColumns = "IndividualSex")
 expect_warning(psuEst <- RstoxFDA:::AnalyticalPSUEstimate(ss, sexStrat, "IndividualRoundWeight", c("IndividualSex")), "Not all strata are sampled. Estimates will not be provided for some strata for SampleIds:")
 psuEst <- RstoxFDA:::LiftStrata(psuEst)
-expect_error(popEst <- RstoxFDA:::AnalyticalPopulationEstimate(stationDesign, psuEst), "Cannot estimate. Estimates are not provided for all samples in 'AnalyticalPSUEstimateData'. Missing for SamplingUnitIds:")
+expect_error(popEst <- RstoxFDA:::AnalyticalPopulationEstimate(stationDesign, psuEst), "Cannot estimate. Abundance- or total-estimates are not provided for all samples in 'AnalyticalPSUEstimateData'. Missing for SamplingUnitIds")
 
 #Test that Abundance and Frequency are NA for unsampled strata (Domain Sex is Unsampled for strata unkown sex)
 unsampled <- merge(psuEst$Abundance, sexStrat$SampleTable[n==0], by=c("SampleId", "Stratum"))
diff --git a/man/AnalyticalPSUEstimate.Rd b/man/AnalyticalPSUEstimate.Rd
index d006b1e..039663d 100644
--- a/man/AnalyticalPSUEstimate.Rd
+++ b/man/AnalyticalPSUEstimate.Rd
@@ -45,9 +45,6 @@ with the function \code{\link[RstoxFDA]{ComputeIndividualSamplingParameters}}.
 If any strata are specified in the SampleTable of 'IndividualSamplingParametersData' but are not sampled per the SelectionTable
 all estimates will be provided as NAs for this stratum.
 
-Domains that are not present in a sample are not reported, although their estimated abundance and total is zero. Use the function
-\code{\link[RstoxFDA]{LiftStrata}} to infer zero values for unreported domains, and mark unsampled strata as NA.
-
 In general unbiased estimates rely on known inclusion probabilites, and domain definitions that coincides
 with stratification. When the domain definitions are not aligned
 with the stratification, ratio estimates are provided for which unbiasedness is not guaranteed.
diff --git a/man/processPropertyFormats.Rd b/man/processPropertyFormats.Rd
index 4b9c915..a279d5b 100644
--- a/man/processPropertyFormats.Rd
+++ b/man/processPropertyFormats.Rd
@@ -5,7 +5,7 @@
 \alias{processPropertyFormats}
 \title{Define the process property formats for inclusion in stox UI}
 \format{
-An object of class \code{list} of length 27.
+An object of class \code{list} of length 28.
 }
 \usage{
 processPropertyFormats
diff --git a/man/stoxFunctionAttributes.Rd b/man/stoxFunctionAttributes.Rd
index d7e5207..35d48df 100644
--- a/man/stoxFunctionAttributes.Rd
+++ b/man/stoxFunctionAttributes.Rd
@@ -5,7 +5,7 @@
 \alias{stoxFunctionAttributes}
 \title{Function specification for inclusion in StoX UI}
 \format{
-An object of class \code{list} of length 65.
+An object of class \code{list} of length 66.
 }
 \usage{
 stoxFunctionAttributes