Scientific Basis
This IBM models adult Atlantic salmon (Salmo salar) migration through the Curonian Lagoon, the largest European coastal lagoon, from Klaipėda Strait to spawning grounds in the Nemunas River basin. The model integrates hydrodynamic forcing, bioenergetics, and estuary-specific stressors based on the following scientific foundations.
Hydrodynamics & Salinity
The Curonian Lagoon is microtidal; exchange is dominated by wind- and pressure-driven flows through Klaipėda Strait with frequent two-layer structure (surface outflow, bottom inflow). Salinity intrusions decay within ~20 km from the sea, with strong vertical gradients near the strait. Movement rules and calibration targets explicitly reflect two-directional flow that toggles with wind and sea-level set-up.
Bioenergetics Model
Wisconsin bioenergetics model for non-feeding migrants (consumption C=0). Respiration parameterized per Forseth et al. (2001) for Salmo salar: RA=0.00264, RB=−0.217, RQ=0.06818. Energy density below 4.0 kJ/g triggers mortality (Snyder et al. 2019). Osmoregulation cost multiplier m_osmo(S) adds energy penalties in brackish waters above tolerance.
Eutrophication & Hypoxia
The system is hypertrophic with recurring cyanobacterial "hyperblooms" that promote transient hypoxia and internal P regeneration. The IBM includes hypoxia-avoidance rules with lethal/high DO thresholds reflecting field-observed feedbacks during bloom-heat-calm episodes.
Seiches & Meteotsunamis
Klaipėda port experiences hazardous long-wave oscillations (harbor seiches, meteotsunami-like events) causing rapid current reversals. The "seiche-pause" trigger delays fish movement when |dSSH/dt| exceeds a threshold, preventing unrealistic transport during extreme oscillation events.
Water Renewal & Connectivity
Lagoon-wide water renewal varies with Nemunas discharge and prevailing wind regimes. Discharge largely sets residence times, while wind controls north-south exchange and internal connectivity. Boundary forcing hooks (Nemunas Q, wind) and validation metrics for seasonal renewal reflect these dynamics.
Forcing Data & Operational Products
The model uses CMEMS Baltic Physics (NEMO v4.2.1, ~2 km, 56 z-levels) for currents, salinity, SSH, and temperature. Wave data is available from CMEMS Baltic Waves. Cross-checking against BOOS multi-model ensembles is supported. Nemunas discharge provides the primary freshwater forcing.
Calibration Targets
Salinity penetration length (~20 km south of Kiaulės Nugara); two-directional flow statistics near the strait; seasonal renewal time sensitivity to discharge and wind; hypoxia exposure timing during bloom/heat/calm spells; port long-wave event frequency (movement pausing under strong dSSH/dt).