MOTE MARINE LABORATORY

Project Title

Geographic comparison of age, growth, reproduction, movement and survival of red snapper off the state of Florida

    As part of MARFIN award # NA17FF2881, entitled “Geographic comparison of age, growth, reproduction, movement and survival of red snapper off the state of Florida,” MML biologists are using “ear stones” or otoliths to age red snapper.

 Otoliths, found in each of the two otic cavities on either side of the fish’s cranium, are made of calcium carbonate, and are part of a boney fish’s normal hearing apparatus. Scientists around the world use otoliths to age fish, because daily rings and more distinctive yearly rings (annuli) are laid down on the otolith.

    The relative size and shape of the otolith is distinctive of the species of fish from which it came. Reef fish tend to have larger thick otoliths, whereas, other species such as billfish and dolphin (mahi-mahi) have very tiny otoliths. To determine the age of the red snapper from the thick opaque otolith, sections of the otolith must be cut and mounted on glass slides. Once this is accomplished, a biologist can use a microscope to see and count the number of rings on the otolith, similar to counting the number of tree rings to determine the age of a tree.

    There has been a lot of good research conducted on red snapper life history in the northern Gulf of Mexico and in the South Atlantic. Much less work has been done on red snapper captured in the central and southeastern Gulf of Mexico and on Florida’s east coast off St. Augustine. Mote biologists are collecting red snapper otoliths from these areas to add to the knowledge of red snapper life history in the Gulf of Mexico and the South Atlantic.

Mote staff and volunteers are also tagging and releasing red snapper in these areas. See the list of goals and objectives for additional details.

Project Goals and Objectives

Goals
▸ To evaluate the use of minimum size limits as a management tool for red snapper.
▸ To characterize and assess the impact of bycatch of red snapper, including release mortality by recreational fishers and recreational-for-hire vessels in the Gulf of Mexico and South Atlantic.
▸ To determine the source of and quantify natural and human-induced mortalities, including release mortality estimates for charter boats, headboats, and private recreational vessels targeting red snapper.
▸ To assess tag performance of plastic single barbed dart tags on red snapper, including tag shedding rate and effects on growth and survival.
▸ To provide data for stock and population assessment for red snapper.

Objectives
▸ To test the hypothesis that red snapper will survive depth induced mortality.
▸ To obtain life history information including age and growth and reproductive data for red snapper off the southwest and northeast coast of Florida and compare these data with those from the northern Gulf of Mexico.
▸ To test the hypothesis that circle hooks will greatly reduce release mortality in red snapper.
▸ To obtain catch and release mortality rates relative to depth and gear for red snapper.
▸ To determine tag shedding rates and effects on growth and survival for red snapper with single barbed dart tags.
▸ To obtain movement and migration patterns for red snapper in the Gulf of Mexico and South Atlantic.

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