Stories of epic fish landings and seas teaming with unfathomable amounts of marine life abound in the ancient folklore of generations past. Fishermen tell stories of schools of fish so dense that you could walk across their backs and not get wet. Hidden between the occasional fish tale lies a wealth of fishery information in the form of old ship logs, tax accounts, literary texts, restaurant menus, and even photographs. Researchers from the UK, the US, New Zealand, and Italy are combing a wide array of unconventional data sources to shed light on the historic sizes, abundance and distribution of marine life over time.

The research is part of the Census’ History of Marine Animal Population (HMAP) project. Through the continued study of historic records and artifacts researchers hope to compile baseline data for species that were well documented throughout history. Population data for commercially hunted species, such as the southern right whale (Eubalaena australis), is so thorough that it has the potential to provide policy makers with a relatively accurate baseline from which to set appropriate environmental goals in the future.

In New Zealand, researchers have utilized over 150 whaling logbooks and additional records to learn more about the southern right whale. A short and well documented history of the island’s southern right whale fishery points to an early 1800’s whale population between 22,000 and 32,000. By 1925, it is estimated with a 95% statistical confidence that a few as 25 reproductive females survived the intense whaling operations taking place on the island. Given that today’s population of 1,000 southern right whales is only a small remnant of what once was, researchers are also questioning what roles these massive animals may have once played in the local ecosystem before they were nearly eradicated by whaling.

Loren McClenachan of the Scripps Institution of Oceanography did not have the luxury of extensive fishery records in her research of reef fish declines in the Caribbean. Instead of scanning logbooks Lauren employed over 50 years worth of “trophy” fish photographs taken by Key West sport fishermen between 1956 and 2007. Lauren’s research revealed decreases in average fish weight and changes in the species of fish being caught. Average fish weight was reduced from an estimated 44 pounds in 1956 to an estimated 5 pounds in 2007. Large predatory species, such as grouper and sharks, initially dominated the catch, but 2007 catches were dominated by small snappers.

The research conducted by these researchers was presented along with additional historic studies at the second annual Oceans Past Conference on 26-28 May. Other topics that were discussed included 2nd century CE Latin and Greek verses pointing towards early Roman trawling efforts, a mid-1800 European herring fishery collapse, and the mid-1800 introduction of exotic periwinkle snails to Nova Scotia from England. The conference will hopefully shed more light on past environmental trends, and in turn provide valuable clues about future marine population dynamics.

• Science Daily