Fish migrate south to warmer waters during the LGM

Archaeozoological finds  of marine and amphihaline fish remains from the Last Glacial Maximum (LGM)  show evidence of very different species ranges compared to the present.

An ecological niche model based on paleoclimatic reconstructions of sea surface temperatures and bathymetry have been used to effectively predict the spatial range of marine fish during the LGM. The results indicate that the ranges of marine fish species now in northwestern Europe were displaced significantly southwards from the modern distribution, challenging an existing paradigm of marine glacial refugia. 

The model presents strong evidence of an invasion of important fish through the Straits of Gibraltar in glacial times, where they were exploited by Palaeolithic populations around the western Mediterranean Sea. Kettle (2010)

The Megalodon Megaselachus megalodon was an enormous shark. It first appeared around 18 million years ago and was found in all oceans of the world from the Miocene until the Mid-Pleistocene.  It became extinct around 1.5 million years ago. It evolved from the Isurus during the Eocene (around 50 million years ago). The first true ancestor was the Carcharocles auriculatus, which was rather smaller. People used to see the Megalodon as ancestor of the modern white shark. It is however, more likely that the Megalodon belongs to a separate genus and is just a distant relative of the modern white shark.

Reconstructed megalodon skeleton 
on display at the Calvert Marine Museum
Solomon, Maryland, USA

This animal dominated the oceans and is regarded one of the largest and most powerful predators of all vertebrate animals to have ever lived. He could reach a length up to 18 metres, dilate its mouth about 2 metres with tail fins  over 4 metres in length and a dorsal fin could reach a length of 2 metres. He had a cosmopolitan distribution, which means that its habitat was spread throughout the entire world, in (almost) every ocean. 

The enormous triangular teeth, with a length of 15 cm (enamel + crown),that have been found, were first believed to be derived from snakes and dragons. It was discovered in 1667, they were in fact, shark teeth.   

Megalodon Tooth

Most fossils are teeth or vertebral columns. Fossils of Megaselachus megalodon have been found near St. Maria Island, the Azores. Avila (2012)

The Sabre-Toothed Salmon (Oncorhynchus rastrosus)
 first appeared near the coast of modern California, during the Miocene, disappearing during the Pleistocene. They travelled up the rivers from the sea to breed. This extinct fish was about 250-300 cm in length. Characteristic for this animal were its fangs, sticking out the tip of its snout. Besides these fangs, the fish had relatively little teeth, which suggests that it ate plankton.

For the eel, this refugium was probably on the Atlantic coasts of Portugal and Morocco.Kettle (2008)  The glacial refuge of the shad is unclear, but remains have been discovered on the upper Tagus River system at Aridos-1 from the Mindel-Riss interglacial approximately 300 ka BP  and  it is likely to have survived the glacial maximum around the Iberian Peninsula and northwest Africa. 

In Southern Spain, the boreal gadid species, haddock Melanogrammus aeglefinus) and pollock (Pollachius pollachius) have been reported for the Cueva de Nerja near Malaga dating to the LGM:  significant because these species are currently found in Northwest Europe, and the southernmost range for haddock and pollock is currently the Bay of Biscay and northern Portugal, respectively. Whitehead (1986)

The most recent analyses of the LGM deposits from the Cueva de Nerja have revealed that the northern gadids (including saithe Pollachius virens, cod Gadus morhua, and ling Molva molva) make up more than 30% of the identified fish remains and thus represented a significant presence among the  fish exploited by Paleolithic hunters with the exploitation of gadids continuing for an extended period of time after the LGM until the early Holocene as sea levels were returning to present levels and sea surface temperatures approached present values.

Atlantic Salmon (Salmo salar)

Among the most spectacular  species range shifts  have been reports of  of Atlantic salmon (Salmo salar) remains in archaeological sites from the Mediterranean drainage basins of France, Spain, and Italy dating from the LGM up to the early Holocene. Additional small art objects unambiguously depicting salmon have been located at the Grand Grotte de Bize on a Mediterranean drainage basin with reports from late Palaeolithic–early Mesolithic sites in France, Spain, and Italy) suggesting  the presence of resident salmon populations in the western Mediterranean Sea.  However recent genetic analysis has shown a mitochondrial DNA variation in Pleistocene and modern Atlantic salmon from the Iberian glacial refugium.

Consuegra (2002)

The current southernmost range of Atlantic salmon in Northwest Europe is Northern Portugal, which indicates that immigrant populations would have had to pass through the Straits of Gibraltar when temperatures in Southern Spain during the LGM were similar to  present day Northern Europe. However, the archaeozoological evidence is contested. Many  sites in southern France are in proximity to Atlantic drainage basins, and it is possible that the Atlantic salmon remains in the Mediterranean watersheds may have been transported as part of a seasonal migration of fishermen.