Table 2 Estimated regression parameters (intercept and slope values) for the Gaussian GAM presented in Eqs. 1, 2 and 3

Model A

log (µ_ij) = 

AUTUMN

0.536 + 0.092 × δ¹⁵N_ij—0.460 × Crustacean_ij + 0.460 × Chironomidae larva_ij + 0.098 × perch juvenile_ij + 0.120 × G. cernua_ij + 0.142 × O. limosus_ij—0.349 × C. harengus_ij + s(Length)_ij

SPRING

0.642 + 0.092 × δ¹⁵N_ij—0.460 × Crustacean_ij + 0.460 × Chironomidae larva_ij + 0.098 × perch juvenile_ij + 0.120 × G. cernua_ij + 0.142 × O. limosus_ij—0.349 × C. harengus_ij + s(Length)_ij

Model B

log (µ_ij) = 

AUTUMN

0.514 + 0.090 × δ¹⁵N_ij + 0.299 × Chironomidae larva_ij + 0.186 × perch juvenile_ij + 0.174 × O. limosus_ij—0.484 × C. harengus_ij + 0.079 × N. melanostomus_ij + s(Length)_ij

SPRING

0.628 + 0.090 × δ¹⁵N_ij + 0.299 × Chironomidae larva_ij + 0.186 × perch juvenile_ij + 0.174 × O. limosus_ij—0.484 × C. harengus_ij + 0.079 × N. melanostomus_ij + s(Length)_ij

Model C

log (µ_ij) = 

AUTUMN

0.529 + 0.091 × δ¹⁵N_ij + 0.233 × Chironomidae larva_ij + 0.167 × perch juvenile_ij + 0.184 × O. limosus_ij—0.501 × C. harengus_ij + 0.023 × N. integer_ij + s(Length)_ij

SPRING

0.649 + 0.091 × δ¹⁵N_ij + 0.233 × Chironomidae larva_ij + 0.167 × perch juvenile_ij + 0.184 × O. limosus_ij—0.501 × C. harengus_ij + 0.023 × N. integer_ij + s(Length)_ij