Rebecca Asch November 1 2007 SIO 277 Challenger Project The History of Grenadier Life History Growth Reproduction and Early Life History of the Family Macrouridae from the Challenger Expedition to Present Day The family Macrouridae which is commonly known as the grenadiers or the rattails contains a total of 386 fish species Froese and Pauly 2007 that share a characteristic elongated body with long dorsal and anal fins supported by numerous fin rays Grenadiers are typically bathydemersal and are found along the continental slope and abyssal plain in all oceans Most grenadiers are nomadic foragers that can act as both predators and scavengers that will can consume benthic prey e g crabs ascidians polychaetes echinoderms foraminifera and even sponge spicules and mid water pelagic organisms e g euphausiids prawns and myctophids Marshall 1964 Gage and Tyler 1991 Compared to other families of deepwater fish the Macrouridae are extremely abundant making up almost 100 of the fish biomass in the northeast Pacific Ocean at depths below 2 000 m Stein and Pearcy 1982 Due to the large volume covered by the deep sea the total biomass of just two macrourid species i e Coryphaenoides armatus and C yaquinae is globally estimated to be 150 million tonnes which is larger than the total annual commercial catch of all marine fishes combined Gage and Tyler 1991 Despite their high numerical abundance and cosmopolitan distribution little is known about the biology of the grenadiers compared to shallow water species of fish This is especially true of grenadier early life history traits reproduction patterns and population age structure Prior to the publication of Volume LVII of the H M S Challenger Reports few species in the family Macrouridae were known and specimens from this group were poorly represented in taxonomic collections The Challenger expedition collected over 140 specimens of macrourid fish belonging to 30 species G nther 1887 While 140 specimens may not sound like many by today s standards these specimens provided some of the first evidence that macrourids were widely distributed and quite abundant at depth in all oceans Based on the new data provided by the Challenger expedition the taxonomic classification of genera in the family Macrouridae was re ordered resulting in the recognition of 46 species belonging to 4 genera G nther 1887 Part of the reason why it was necessary to reorganize the genera in this family was that juvenile and adult life stages of fish belonging to the same species had previously been classified as separate species The collection of 12 species of juvenile macrourids during the Challenger expedition revealed to taxonomists the changes in macrourid morphology that occur as juvenile fish reach maturity thus allowing them to better determine whether juvenile and adult specimens belong to the same or different species While many morphological traits that differed between juveniles and adults were species specific G nther 1887 proposed that the number of spines on the scales of several macrourid species increased during the transition from the juvenile to adult life stages Also the barbs on several species dorsal spines tended to further apart and less numerous in juvenile specimens The only other piece of information on grenadier life history presented in the Challenger report is that the species Trachyrhynchus longirostris likely spawns during the month of July and produces millet sized eggs G nther 1887 Despite of the progress made during the Challenger expedition researchers remained unable to collect any specimens of larval macrourid fish G nther 1887 commented that the absence of grenadier larvae appeared strange given the abundance and diversity of juvenile and adult macrourids that were collected during the expedition For several decades following the Challenger expedition references to macrourid fish in the scientific literature were mainly limited to descriptions of new species and reports documenting the distribution of this family across different geographic regions Increased surveying of the deep sea fishes of the North Pacific during this time period resulted in the discovery of several new species from areas offshore of Japan and the Hawaiian Islands Gilbert and Hubbs 1916 Gilbert and Hubbs 1917 Katayama 1942 Matsubara 1943 During his tenure as a professor at Scripps Institution of Oceanography Carl Hubbs was particularly involved in describing the distribution of Pacific macrourids As was the case with the Challenger Report information included in these early publications on macrourid life history characteristics was mainly limited to what could be divined from incidental collections of juvenile specimens In fact up until the early 1980s there were only two descriptions of pre juvenile macrourid species from the entire North Pacific Stein 1980 Likewise information on macrourid eggs was extremely scarce although Marshall 1964 did contain a brief description of the eggs of the benthypelagic fish Cynomacrurus piriei One of first papers to focus solely on characterizing the larval and juvenile phases of macrourid fish was Stein 1980 This paper contained the first key for identifying larval specimens from the genus Coryphaenoides collected off of the eastern North Pacific Characteristics that Stein 1980 found useful for identifying larval species of macrourids include premaxillatory and dentatory teeth the number of rays on their dorsal and pelvic fins the number gas glands and retia and pigmentation Once larval grenadiers could be identified more consistently to species Stein s research group at Oregon State University as well other research teams began to paste together more information on macrourid larval ecology The eggs of most grenadier species are easily identifiable by raised hexagonal sculpturing on their surface Collette and Kein MacPhee 2002 These eggs have a large oil globule which makes them buoyant After being spawned and fertilized at depth the buoyant macrourid eggs float upwards into the area above the seasonal thermocline Gage and Tyler 1991 Once the eggs hatch larval grenadiers are retained in pelagic habitats where they consume copepods as their primary prey Merrett 1978 Metamorphosis between the larval and juvenile stages occurs once an individual reaches approximately 10 15 mm HL head length Stein 1980 The rapid metamorphosis phase is characterized by loss of the peduncle on the pectoral fin changes in the angle of the mouth the