Authors: J.S. Rogers, J.A. Hare, D.G Lindquist

Jason Rogers

Otolith record of age, growth, and ontogeny in larval and pelagic juvenile Stephanolepishispidus (Pisces: Monacanthidae)

Authors: J.S. Rogers, J.A. Hare, D.G Lindquist

1)Introduction

a)Larval fishes and survival

i)Adult fish populations fluctuate due to process on the larval level

ii)Duration of larval stage and growth rate can impact survival rates

iii)Processes that effect growth and development in the early life history of fishes should be studied

b)Otoliths

i)Otoliths are used as chronometers for fish age and growth (include figures 2a & 2b)

ii)Otoliths used to discern different life history stages

(1)First feeding, yolk-sac absorption and the timing of the larval-juvenile transition

c)Sargassum and Stephanolepishispidus information

i)Fishes which use Sargassum as habitat

(1)Juvenile S. hispidus dominates Sargassum habitat

ii)S. hispidus distribution

iii)S. hispidus reproduction habits and adult habitats

d)Goals of the study

i)Examine otolith record for age, growth and ontogeny for S. hispidus

ii)Understand the recruitment process on juvenile fishes in Sargassum

iii)Understand the early life history of S. hispidus

2)Materials and methods

a)Rate of increment formation

i)Laboratory reared fish

(1)Date and area of wild fish collection

(2)Procedures used for alizarin immersion, rearing and feeding

ii)Otolith examination

(1)Otolith examination and microscopy techniques

(2)Linear regression compared to a slope of 1.0

b)Otolith record of age, growth and development

i)Sample collection and otolith preparation

(1)Dates, areas and gear used for sample collection (include figure 1)

(2)Morphology and meristics for individual fish (include drawing of both adult and larval fish)

(a)Notochord length and standard length

(b)Body depth measurements

(c)Enumeration of dorsal and anal fin rays

ii)Relationships between otolith size, fish length, and age

(1)Regression models

(2)Techniques used to select appropriate models

iii)Age at larval to juvenile transition

(1)Increment width to discern transition

(2)Evaluation of size distribution throughout the water column

(3)Piecewise regression models

3)Results

a)Validation of increment formation (include table 1)

b)Otolith size, fish size, and age relationships

i)Figure 3A-C

ii)Range of ages and models selected for use

c)Age at larval to juvenile transition

i)Larger fish found at the surface and smaller fish found at the bottom (figure 5A,B)

ii)Transition occurs at approximately 8mm and 18 days

iii)Using piecewise regression on meristic data shows transition at about 18 days (include figure 6A-C)

iv)Otolith increment width on the population level and the larval to juvenile transition

4)Discussion

a)Validation of increment formation

i)Increment formation is daily

ii)Other daily increment formation studies

b)Length, otolith size and age relationships

i)Comparison with P. scaber

ii)S. hipidus growth rates compared with other species

c)Larval to juvenile transition

i)Larval to juvenile transition concerning meristics and a change in body depth

ii)Larval to juvenile transition results in a habitat shift

iii)Sargassum and its importance as juvenile habitat