library(tidyverse)
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library(here)
## here() starts at C:/Users/zacka/OneDrive/Desktop/142CL/Lab4

Overview

Spiny Lobsters (Panulirus argus) are an essential piece of economic trade throughout the Caribbean, and have been ranked as the most important commercial invertebrate in the region. These organisms live on shallow shelves on the ocean floor and are primarily harvested by traps and diving methods. In addition, Caribbean spiny lobster also have one of the longest pelagic larval durations, making this species’ population dynamics fluctuate between regions.

In this report, we will be studying the catch, abundance, and recruitment of spiny lobsters throughout the Caribbean. This information is critical for sustainable fishery management and for maintaining spiny lobster populations in different areas of the Caribbean. Protective legislation can result from this study, as well as regulations to sustain and assist lobster populations with growth. This study can also act as a springboard to provide further study into the population dynamics of Caribbean spiny lobsters.

Lobster populations experience large amounts of fishing pressure as well as significant differences in catch and abundance across regions. Previous studies have predicted that ocean currents will move lobster populations along a current’s path due to the species’ long pelagic larval duration (Butler VI et al. 2009). We hypothesize that Puerto Rico will have the highest lobster catch, egg abundance, and recruitment due to being the largest island and being located furthest downstream of the North Atlantic Current. A previous study showed that the Puerto Rican lobster community is under high fishing pressure, which also supports our hypothesis (Mateo 2004). This paper will continue the work done by previous studies and evaluate modern lobster communities to provide guidance for protective fishery legislation. We will achieve this by using NOAA landings data to take a close look at lobster catch and egg abundance from 1975-2017.

Data Summary and citation

NOAA Fisheries. 2024. Stock SMART data records. Retrieved from apps-st.fisheries.noaa.gov/stocksmart. 05/15/2024.

Butler IV, Mark J., et al. “Patterns of Spiny Lobster (Panulirus argus) Postlarval Recruitment in the Carribbean: A CRTR Project.” (2009). https://digitalcommons.odu.edu/biology_fac_pubs/79/

Mateo, Ivan. “Population dynamics for spiny lobster Panulirus argus in Puerto Rico: a progress report.” (2004). http://hdl.handle.net/1834/29591

knitr::opts_chunk$set(
    echo = TRUE,
    message = FALSE,
    warning = FALSE
)
#load necessary packages

library(tidyverse)
library(here)
library(ggplot2)

Lobster Catch

PreppedLobsterChar1 <- read.csv("C:/Users/zacka/OneDrive/Desktop/142CL//PreppedLobsterChar1.csv")


LobsterCatch <- ggplot(PreppedLobsterChar1, aes(x=Year, y=Catch_Metric_tons, group =Name, color =Name))+
  geom_line()+
  theme_minimal()+
  scale_colour_brewer(palette = "Set1")+
  labs(x = "Year", y = "Catch (metric tons)", title = "Lobster Catch", caption = "Fig1: NOAA data displaying 
  catch of spiny lobster in Puerto Rico, Saint Croix, and St. Thomas/St. John
        (1975-2017).")

LobsterCatch

Puerto Rico is the primary lobster landing site in the Caribbean. Saint Croix began with less landings in the late 20th century, and experienced a small catch boom in the 2000s but is returning to its normal sub-20 metric ton catch. St. Thomas/St. John also experienced a small boom in the early 2000s but has continued to steadily increase.

Lobster Egg Abundance

library(tidyverse)
library(ggplot2)
library(here)


LobsterAbundance <- ggplot(PreppedLobsterChar1, aes(x=Year, y=Abundance_Thousand_eggs, group =Name, color =Name))+
  geom_line()+
  theme_minimal()+
  scale_colour_brewer(palette = "Set1")+
  labs(x = "Year", y = "Egg Abundance (thousands)", title = "Lobster Egg Abundance", caption = "Fig2: NOAA data displaying abundance of spiny lobster eggs in Puerto Rico, Santa Cruz, and 
       St. Thomas/St. John. (1975-2017).")

LobsterAbundance

Puerto Rico had very few eggs but quickly rose to the highest in the region in the mid 1980s. As Puerto Rico egg numbers continue to rise and stay high while other regions (such as Saint Croix and St. Thomas/St. John) decline, Puerto Rico remains the primary focus for lobster harvesting. Fisheries should concentrate their efforts here, but not exceed MSY. Egg number is increasing in Saint Croix, which can reflect population recovery or less fishery activity in these regions.

Recruitment Variance between Regions

ggarrange(PuertoRicoBox, SaintCroixBox, STSJBox, 
          ncol = 3, nrow = 1, common.legend =TRUE)

Puerto Rico and St. Croix typically have recruitment on the higher end, with a tapering tail towards the low side. Meanwhile, St. Thomas/St. John have a more evenly distributed recruitment pattern, but still has a tapering tail toward the lower end. This indicates that recruitment can often be expected near the median value or slightly higher, but years that are below the median can be much lower than expected. In other words, there can be more extreme “drought” years with less new lobster recruited and less extreme “peak” years with more new lobster recruited.

Statistical Testing

Here, we are going to test the variation of spiny lobster catch across the two similar regions of Saint Croix and St. Thomas/St. John. It is clear that Puerto Rico has a much higher mean catch per year, so it will be more helpful to examine if a statistically significant difference exists between the two closer populations of Saint Croix and St. Thomas/St. John. Null Hypothesis: There is no significant difference between the two locations. Alternative Hypothesis: There is a significant difference between the two locations.

TtestLobster3 <- read.csv("C:/Users/zacka/OneDrive/Desktop/142CL//TtestLobster3.csv") 

t.test(Catch ~ Group, data = TtestLobster3)
## 
##  Welch Two Sample t-test
## 
## data:  Catch by Group
## t = -2.1111, df = 75.052, p-value = 0.03809
## alternative hypothesis: true difference in means between group 2 and group 3 is not equal to 0
## 95 percent confidence interval:
##  -19.6114002  -0.5689676
## sample estimates:
## mean in group 2 mean in group 3 
##        25.89731        35.98749

As a result of the p-value being 0.03809 (which is below 0.05), we can reject our null hypothesis. This means we can say with 95% confidence that there is a significant difference in catch between Saint Croix and St. Thomas/St. John.

Conclusions

Similarly to what Mateo found in 2004, we found spiny lobster catch and egg abundance to be highest in Puerto Rico (Fig. 1, Fig. 2). In addition, these results backed up our hypothesis that ocean currents could transport lobsters to Puerto Rico through the North Atlantic current.

In order to best direct fishing efforts, we also found that Saint Croix has a higher catch rate than St. Thomas/St. John, which could also result from being further downstream of the North Atlantic current despite being of comparable island size.

These results support what exists in the field, with populations reflecting the influence of ocean currents as well as island size (Butler VI et al. 2009). As more studies are conducted on this region, emphasis should be on egg abundance, as it directly influences catch and can provide standards for sustainable fishing practices. By predicting egg abundance through modelling, trapping efforts can be best tailored to each region. In addition, if egg abundance is predicted to decline, MPAs or other regaultions can be put into place to prevent population crashes.