Latitudinal Differences in the Biology of the Foxfish Bodianus Frenchii, An
Total Page:16
File Type:pdf, Size:1020Kb
Biology of the Foxfish Bodianus frenchii, an exceptionally long-lived, monandric protogynous labrid, including regional comparisons Travers, M.J., Potter, I.C., Clarke, K.R., Newman, S.J. and Hutchins, J.B. (2009) Latitudinal and bioregional patterns of fish assemblages in north-western Australia. In: 8th Indo Pacific Fish Conference and 2009 ASFB Workshop and Conference, 31 May - 5 June 2009, Fremantle, Western Australia. Steve Cossington, Alex Hesp & Ian Potter Photo : Barry Hutchins Bodianus frenchii • Medium-sized (480mm TL) temperate labrid • In sub-genus Verreo, which contains 7 temperate Bodianus species • Excellent eating and thus targeted by recreational fishers • Unusual disjunct distribution in southern half of Australia • Environment of lower west and south coasts of WA differ Photo : Barry Hutchins Some characteristics of labrids • Very speciose family • Found in both temperate and tropical waters and often over reefs • Species mainly short lived • Maximum age is 70 years for the temperate Achoerodus gouldii • Many species are protogynous hermaphrodites, i.e. change sex from female to male • Carnivorous Ageing of Bodianus frenchii • Number of opaque zones in sectioned otoliths • Marginal increment analysis validated that a single opaque zone is formed annually in otoliths • Schnute growth curves fitted to lengths at age Whole otolith Sectioned otolith Periphery of otolith Age and Growth 500 South coast Maximum age is 78 years! 400 Several fish > 50 years old 300 Rapid initial growth on both coasts West coast 200 Lengths at age typically 100 greater on the south than Total length (mm) west coast 0 0 10 20 30 40 50 60 70 80 Age (years) the south coast south the coasts both mm > 237 fish in mature 100% years, mm> 279 fish in 100% mature years, Reflects faster growth on south coast south on growth faster Reflects on age younger a at attained Maturity on lengths similarat attained Maturity L coast South L westcoast Lower 50 50 = 236mm , 50% mature by 4 by ,mature 50% = 236mm = 245mm, 50% mature by 8 by mature 50% = 245mm, Lengths and ages at maturity at ages and Lengths - 9 - 5 West coast South coast 13 0 0 0 2 3 3 2 4 5 8 3 3 4 16 17 20 14 0 0 0 1 0 3 2 2 1 1 5 9 10 9 5 17 33 100 0 80 60 40 20 Percentage frequency Percentage 0 0 0 40 80 40 80 120 160 200 240 280 320 360 120 160 200 240 280 320 360 > > Total length (mm) Total length (mm) West coast South coast 4 13 10 3 5 2 4 2 9 12 8 7 5 7 8 9 100 1 10 7 7 3 3 8 2 9 10 3 1 3 6 6 11 80 60 40 20 Percentage frequency Percentage 0 0-1 0-1 >30 >30 10-11 20-21 10-11 20-21 Age (years) Age (years) L 245mm,male= smallest coastSouth L 291mm,male= smallest coastwestLower ageandlength bothmalesof prevalencewith increasingStrongtrendin than length than to moreage related change Sex 0.001) ( coast the south on length a at greater attained change Sex ( coasts both on at similar attained ages change Sex 50 50 = 365mm , = 365mm = 327mm, Lengths and ages at sex change sex at ages and Lengths A A 50 50 p = 28.7 years, = 28.7 > 0.05) = 29.2 years = 29.2 p < West coast South coast 0 0 0 1 1 2 3 2 3 2 3 11 15 21 18 20 30 37 44 41 31 9 100 0 0 0 2 3 3 2 4 5 8 3 3 5 26 34 54 73 45 24 12 5 4 80 60 40 20 Percentage frequency Percentage 0 0 0 40 80 40 80 120 160 200 240 280 320 360 400 440 120 160 200 240 280 320 360 400 440 Total length (mm) Total length (mm) West coast South coast 28 33 23 43 22 28 26 16 12 13 8 8 5 100 26 10 8 44 43 56 51 16 20 8 11 5 3 80 60 40 20 Percentage frequency Percentage 0 0-5 0-4 >60 >60 10-14 20-24 30-34 40-44 50-54 10-14 20-24 30-34 40-44 50-54 Age (years) Age (years) Protogyny • Length by which all females are mature is less than the length of the smallest male • This provides strong evidence that Bodianus frenchii is a monandric protogynous hermaphrodite Bisexual gonad Testis Spawning season and reproductive investment • Spawning season on both coasts is from October to February • Gonad weights during spawning season far greater on south than west coast • Reflected in far greater batch and potential annual fecundities Females - West coast Females - South coast 7 9 8 15 22 16 20 9 6 1712 5 18 1813 1914 28 9 13 11 9 7 25 100 25 100 Legend: ovarian stages 20 80 20 80 Developing/Maturing 15 60 15 60 Mature/Spawning 10 40 10 40 Percent Percent Spent/Recovering 5 20 5 20 0 0 0 0 Standardised gonad weight (g) weight gonad Standardised J A S O N D J F M A M J (g) weight gonad Standardised J A S O N D J F M A M J Month Month Main findings for Bodianus frenchii • Exceptional longevity. Max. age = 78 years • Maturity is related more to length than age • Sex change is related more to age than length • Monandric protandrous hermaphrodite • Regional differences in • Growth • Length and age at maturity and sex change • Fecundity • South coast may provide better environment for growth and reproduction Acknowledgments • Peter Coulson for help with collection of fish • John Stuart for collection tips and local knowledge around Esperance • Gordon Thompson for the preparation of all histological slides.