liminfoFish Identification
Free reference guide: Fish Identification
About Fish Identification
The Fish Identification Reference is a field-guide-style reference covering major Korean saltwater and freshwater fish species along with key morphological identification criteria. It includes detailed profiles for species such as Red Sea Bream (Pagrus major), Yellowtail (Seriola quinqueradiata), Korean Rockfish (Sebastes schlegelii), Olive Flounder (Paralichthys olivaceus), Crucian Carp (Carassius auratus), Largemouth Bass (Micropterus salmoides), Mandarin Fish (Siniperca scherzeri), and Cherry Salmon (Oncorhynchus masou masou).
Beyond individual species profiles, this reference provides systematic identification criteria organized by morphological features: scale types (cycloid, ctenoid, ganoid, placoid), fin types and counting methods (dorsal, anal, pectoral, pelvic, caudal, adipose), body shape classifications (fusiform, compressed, depressed, anguilliform, globiform), lateral line presence and morphology, and tooth types correlated with feeding habits (canine, incisor, molar, villiform, pharyngeal).
The reference also covers fish physiology fundamentals including osmoregulation differences between freshwater and saltwater fish, gill respiration structure with counter-current flow, swim bladder types (physostome vs. physoclist), spawning classifications (demersal, pelagic, adhesive, viviparous), age estimation methods using scales, otoliths, vertebrae, and fin rays, and systematic classification from jawless fishes through cartilaginous to bony fishes.
Key Features
- Profiles 14 major Korean fish species with scientific names, family classification, body shape, coloration, habitat depth, and maximum size
- Covers saltwater species: Red Sea Bream, Yellowtail, Korean Rockfish, Olive Flounder, Chub Mackerel, Horse Mackerel, Black Sea Bream, and Japanese Sea Bass
- Covers freshwater species: Crucian Carp, Common Carp, Largemouth Bass, Mandarin Fish, Cherry Salmon, and Far Eastern Catfish
- Explains fish scale types (cycloid, ctenoid, ganoid, placoid) and their use in age estimation through growth rings
- Details fin counting notation (e.g., D.XII-14) and all fin types including the adipose fin characteristic of salmonids
- Covers fish physiology: osmoregulation, gill counter-current respiration, swim bladder types, and spawning classifications
- Includes age estimation methods using otolith microstructure, scales, vertebral cross-sections, and operculum growth lines
- Documents systematic classification from Agnatha (jawless) through Chondrichthyes (cartilaginous) to Actinopterygii (ray-finned) and Sarcopterygii (lobe-finned)
Frequently Asked Questions
What fish species are covered in this identification reference?
The reference covers 14 major Korean species across saltwater and freshwater categories. Saltwater species include Red Sea Bream (Pagrus major), Yellowtail (Seriola quinqueradiata), Korean Rockfish (Sebastes schlegelii), Olive Flounder (Paralichthys olivaceus), Chub Mackerel, Horse Mackerel, Black Sea Bream, and Japanese Sea Bass. Freshwater species include Crucian Carp, Common Carp, Largemouth Bass, Mandarin Fish, Cherry Salmon, and Far Eastern Catfish.
How can I distinguish Crucian Carp from Common Carp?
The key distinguishing feature is barbels: Common Carp (Cyprinus carpio) has 2 pairs (4 total) of barbels near the mouth, while Crucian Carp (Carassius auratus) has no barbels at all. Both belong to the Cyprinidae family but can be reliably separated by this single morphological trait.
What are the four main fish scale types?
Cycloid scales are smooth and round, found on soft-rayed fishes. Ctenoid scales have comb-like projections on the posterior edge, found on most spiny-rayed bony fishes. Ganoid scales are diamond-shaped, found on sturgeons and gars. Placoid scales are tooth-like, found on sharks and rays. Scale growth rings (annuli) can be counted to estimate fish age.
How does the fin counting notation work?
Fin formulas use Roman numerals for spiny rays (hard) and Arabic numerals for soft rays. For example, D.XII-14 means the dorsal fin has 12 spiny rays and 14 soft rays. The notation system covers dorsal (D), anal (A), pectoral (P), pelvic (V), and caudal (C) fins. The adipose fin, characteristic of salmonids, is a small fleshy fin without rays.
What is the difference between physostome and physoclist swim bladders?
Physostome swim bladders are connected to the esophagus via a pneumatic duct, allowing the fish to gulp or release air (found in carp and salmon). Physoclist swim bladders have no duct connection and use a gas gland and oval body to regulate buoyancy (found in perch and sea bream). Some fish like sharks, rays, and benthic flatfish lack swim bladders entirely.
How do freshwater and saltwater fish differ in osmoregulation?
Freshwater fish have body fluid concentrations higher than the surrounding water (hypotonic environment), so they absorb ions through gills and excrete large volumes of dilute urine. Saltwater fish have body fluid concentrations lower than seawater (hypertonic environment), so they drink seawater, excrete NaCl through gills, and produce concentrated urine. Euryhaline species like salmon and eels can transition between both environments.
What methods are used for fish age estimation?
The most common methods include: scale reading (non-destructive, counting annuli), otolith analysis (most accurate, using daily and annual growth rings), vertebral cross-sections, fin ray cross-sections, and operculum growth line counting. Otolith microstructure analysis can even estimate age in days by counting daily growth increments.
Why is Largemouth Bass classified as an invasive species in Korea?
Largemouth Bass (Micropterus salmoides) was introduced to Korean lakes and reservoirs but is now designated as an ecosystem-disrupting species. It is a voracious predator with a large mouth (upper jaw extending past the eye) that feeds on native fish populations. Its rapid reproduction and competitive advantage have negatively impacted native freshwater fish diversity.