Your example is not actually reproducible because you are not providing the data within the reprex itself, and you are not including library calls.
I think this is what you are trying to do
library(tidyverse, quietly = TRUE)
YearsPooled <- data.frame(stringsAsFactors=FALSE,
Year = as.factor(c(2015, 2015, 2015, 2015, 2015, 2015, 2015, 2015, 2015,
2015, 2015, 2015, 2016, 2016, 2016, 2016, 2016, 2016,
2016, 2016, 2016, 2016, 2016, 2016, 2016, 2016, 2016,
2016, 2016, 2016, 2016, 2016, 2016, 2016, 2017, 2017,
2017, 2017, 2017, 2017, 2017, 2017, 2017, 2017, 2015, 2015,
2015, 2015, 2015, 2015, 2015, 2016, 2016, 2016, 2016,
2016, 2016, 2016, 2016, 2016, 2016, 2016, 2016, 2016,
2016, 2016, 2016, 2016, 2016, 2017, 2017, 2017)),
Lake = c("A6", "A6", "A6", "A6", "A6", "A8", "A8", "D7", "D7",
"D7", "D7", "D7", "A6", "A6", "A6", "A8", "A8", "A8",
"A8", "A8", "A8", "B2", "B2", "B2", "B2", "B2", "B2",
"D7", "D7", "D7", "D7", "D7", "D7", "D7", "B2", "B2",
"B2", "B2", "B2", "D7", "D7", "D7", "D7", "D7", "A6", "A8",
"A8", "D7", "D7", "D7", "D7", "A6", "A6", "A6", "A6",
"A6", "A8", "A8", "A8", "A8", "A8", "A8", "A8", "B2",
"B2", "D7", "D7", "D7", "D7", "A6", "B2", "D7"),
LogWeight = log(c(0.0915, 0.166, 0.201, 0.1416, 0.1913, 0.365, 0.534,
0.182, 0.1951, 0.2137, 0.2729, 0.3845, 0.0534, 0.7558,
0.6106, 0.1219, 0.1249, 0.2519, 0.4617, 0.415, 0.9104,
0.0643, 0.0807, 0.1435, 0.0292, 0.0689, 0.923, 0.706,
0.761, 0.506, 0.579, 0.689, 0.562, 0.6049, 0.264, 0.3025,
0.2666, 0.3032, 0.3573, 0.6741, 0.7112, 0.7173, 0.7104,
0.9858, 0.5854, 0.5298, 0.8723, 0.5171, 0.55, 0.659,
0.5147, 1.3292, 0.3911, 0.696, 0.9489, 0.6278, 0.1397,
0.2709, 0.72, 0.6535, 0.8723, 0.9278, 1.1383, 0.13, 1.1902,
0.2864, 0.4656, 0.3965, 1.1652, 1.7541, 0.8721, 0.5807)),
LogLength = log(c(29, 34, 36, 33, 35, 41, 48, 35, 34, 34, 39, 44, 24,
48, 48, 29, 31, 37, 45, 42, 51, 24, 27, 30, 19, 23,
52, 48, 54, 53, 57, 47, 55, 51, 35, 37, 36, 37.5, 41, 53,
49, 51, 50, 59, 47, 48, 51, 46, 47, 46, 46, 61, 45, 47,
55, 44, 34, 35, 51, 49, 53, 57, 57, 36, 57, 42, 41, 45,
58, 68, 54, 55)),
K = c(0.375169134, 0.42234887, 0.430812757, 0.394022873,
0.446180758, 0.529591852, 0.482855903, 0.424489796,
0.496387136, 0.543710564, 0.460054957, 0.451375845,
0.386284722, 0.683412905, 0.552119502, 0.499815491,
0.419254137, 0.497305194, 0.506666667, 0.560144693, 0.686312203,
0.465133102, 0.409998476, 0.531481481, 0.425718035,
0.566285855, 0.656434911, 0.638382523, 0.483285068,
0.339877886, 0.312646806, 0.663629446, 0.337791134, 0.456008624,
0.61574344, 0.597200561, 0.571416324, 0.574957037,
0.51841964, 0.452789887, 0.604510026, 0.540742248, 0.56832,
0.479990651, 0.563844235, 0.47905816, 0.657590218,
0.531252568, 0.529747744, 0.677036246, 0.528786883,
0.585599676, 0.429190672, 0.67037169, 0.570338092, 0.736992863,
0.35543456, 0.631836735, 0.542777665, 0.555465835,
0.58591992, 0.500990858, 0.614656062, 0.278635117, 0.642680879,
0.386567325, 0.675556071, 0.435116598, 0.597195457,
0.557863067, 0.553840878, 0.349030804),
Parasites = as.factor(c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1))
)
ggplot(YearsPooled, aes(x=LogLength, y=LogWeight, colour=Year, linetype=Parasites)) +
geom_point(size=2, aes(shape = Lake)) +
stat_smooth(method = "lm", col = "black", size=0.25, se=FALSE, fullrange=TRUE) +
theme_bw() +
theme(plot.background = element_blank(), panel.grid.minor = element_blank(), panel.border = element_blank()) +
theme(axis.line = element_line(color = 'black')) +
guides(shape=guide_legend(title=NULL), linetype=guide_legend(title=NULL)) +
scale_color_grey("Year") +
xlab("Length ln(mm)") +
ylab("Weight ln(g)") +
scale_shape_manual("Lake", values=c(15,16, 17, 18)) +
NULL
Created on 2019-01-28 by the reprex package (v0.2.1)