Biology 450: Fish Week Lecture 11: Ontogenetic shifts and dispersal Scott Heppell Department of Fisheries and Wildlife Oregon State University 042 Nash Hall ,

Ontogenetic shifts Fishery Biology Fall 2006 Ontogeny: The entire development of an organism, from fertilization through maturity

The salmon life cycle

More than salmon …

© Richard Herrmann, Poway, California, More than benthic species…

Types of ontogenetic shifts Habitat/location/migration Reproductive strategy Diet Behavior

Ontogenetic shifts: change in lifestyle associated with growth and development Growth rates in habitat x slow, so make a shift to habitat y Growth rates in habitat x slow, so make a shift to habitat y Maximize growth, minimize mortality risk:  /g Maximize growth, minimize mortality risk:  /g Major shifts common in species with very large changes in body size Major shifts common in species with very large changes in body size – Larvae – Juveniles – Increase in depth with body size – Adults – Spawning adults

Why switch habitats? (Werner and Gilliam 1984) Body size Habitat A Habitat B Growth Rate (mm/day) Optimal switching point

Body size Habitat A Habitat B Mortality risk/growth rate (  /g) Want to minimize mortality (  ) AND maximize growth (g)

Loggerhead sea turtle growth curve (mark recapture estimates or width of growth rings on humerus) AGE Length Pelagic Benthic juvenile Subadult Adult

Migration 3 Types Local and seasonal movements Dispersals True migrations Definition: Definition: a move from one place to another

Larvae: pelagic Smalljuveniles: estuaries, estuaries, kelp forests kelp forests Larger juveniles: nearshore reefs nearshore reefs Adults:deeperreefs

1. Local and Seasonal Movements Involves short or long distanceshort or long distance seasonal to semi- diurnal time periodsseasonal to semi- diurnal time periods horizontal or vertical movementshorizontal or vertical movements

Migratory records Mather (1962) tagged two bluefin on June 1 and June 10 in waters off the Bahamas. On September 28 and October 6, respectively, these two fish were recovered near Bergen, Norway nm

2. Dispersal Includes Passive or active movement away from the breeding habitat over a wide area (e.g., larval transport, juvenile dispersal)Passive or active movement away from the breeding habitat over a wide area (e.g., larval transport, juvenile dispersal) Ontogenetic shifts between habitatsOntogenetic shifts between habitats

Involves Directed movement between widely separated and well-defined areas, often at set times during the year (e.g., feeding to breeding areas)Directed movement between widely separated and well-defined areas, often at set times during the year (e.g., feeding to breeding areas) Often ignores local conditionsOften ignores local conditions 3. ‘True’ Migration

Why migrate? BreedingBreeding –Aggregations for mating/spawning –Optimal birthing/nesting areas

Why migrate? BreedingBreeding –Aggregations for mating/spawning –Optimal birthing/nesting areas FeedingFeeding –Higher latitudes = more food more food –Food patches often ephemeral

Migration to Spawning Sites & Passive or Active Larval Migration Improve breeding success Reduce impact of environmental fluctuations Larval Dispersal Cushing’s (1957) match-mismatch hypothesis

Evolutionary Perspective Migration involves specialized behaviors that have arisen through natural selection How do we think about this? Trade Offs: Costs versus Benefits

Benefits Increased feeding opportunitiesIncreased feeding opportunities Avoidance of adverse environmental conditionsAvoidance of adverse environmental conditions Improved current reproductive successImproved current reproductive success Energetic cost of migration itselfEnergetic cost of migration itself Increased predation risksIncreased predation risks Energetic & development costs of any specific migratory adaptationEnergetic & development costs of any specific migratory adaptation Potential reproductive costs due to decreased lifetime reproductive effortPotential reproductive costs due to decreased lifetime reproductive effort Costs

Fitness Probability of survival to age x  l x Multiplied by Fecundity and breeding success  m x Summation of: Migration favored if:  l x m x migrators >  l x m x residents

Migration - Maturation Decision Given that migration is costly and potentially dangerous, age or size at maturity may be delayed Some species (some rockfish, sturgeon, others?) appear to go through a “false maturation” in which females physiologically prepare for reproduction but resorb their eggs instead of completing maturation

Migratory Patterns Oceanodromous Diadromous Potamodromous

Diadromy Gross ‘87

McDowall ‘87

Gross et al. ‘88

Migration pathways of large pelagics Can follow physical features, such as continental margins or major currentsCan follow physical features, such as continental margins or major currents However, “corridor” concept probably too simplifiedHowever, “corridor” concept probably too simplified –Individual variability –Variation in response to ocean conditions Behavior depends on species, time of year, sex, other factorsBehavior depends on species, time of year, sex, other factors –Coastal, pelagic –Direct, stop-and-feed Moving oases of food resources requireMoving oases of food resources require behavioral plasticity behavioral plasticity

Movements of Leatherback Sea Turtles in the Atlantic Ocean as Determined Using Satellite Transmitters

Hector Barrios-Garrido NOAA Why might understanding migration pathways be important from a management perspective?

Legend: 1998, 1999, Early Jettison March/April May June July Lutcavage et al. ‘99

Oceanodromous (European Sea Bass, Dicentrarchus labrax) Overwintering Spawning

Aggregation spawning

Why aggregate? Access to mates Multiple fertilizations Environmental conditions Reduced offspring mortality

Management Ontogenetic shifts in habitat type dictate that habitat protections be in place for all life stagesOntogenetic shifts in habitat type dictate that habitat protections be in place for all life stages Highly migratory species do not care about EEZ lines - international cooperation and research is requiredHighly migratory species do not care about EEZ lines - international cooperation and research is required Bycatch in high seas fisheries presents a management and monitoring problem – need for integration among groupsBycatch in high seas fisheries presents a management and monitoring problem – need for integration among groups –Impact may be large but diffuse and therefore difficult to measure

Options? Fishing and bycatch quotasFishing and bycatch quotas Gear modificationGear modification ClosuresClosures –Spatial, temporal –Requires consideration of entire life cycle, migration of entire life cycle, migration rates and habitat use rates and habitat use –Requires careful consideration of redistribution of effort and of redistribution of effort and markets markets

Modeling movement for reserve planning Understanding of: –Movement patterns –Reproductive strategy –Location of impacts –Suite of management options

Types of movement Habitat A Habitat B “reserve” “leaking” = stochastic movement

Types of movement Habitat A Habitat B “reserve” “spill-over” = density- dependent leaking

Types of movement Habitat A Habitat B “reserve” “seeding” = larval transport

Types of movement Habitat A Habitat B “reserve” “ontogenetic shift” = deterministic movement between habitats due to life stage transition

NewbornjuvenileAdult NewbornjuvenileAdult Offspring production Survival and growth Spillover or leaking RESERVE NON-RESERVE Life stage with increased survival

Egg/larvaejuvenile Spawning Adult Non-spawn adult Spawning adult Offspring production Survival and growth Spillover or leaking RESERVE NON-RESERVE Ontogenetic shiftSeeding from reserve

Egg/larvaejuvenileAdult juvenile Offspring production Survival and growth Spillover or leaking RESERVE NON-RESERVE Ontogenetic shift

Egg/larvaejuvenileAdult juvenileAdult Offspring production Survival and growth Spillover or leaking RESERVE NON-RESERVE Ontogenetic shift Seeding from reserve

Egg/larvaejuvenileAdult Spawning adult Egg/larvaejuvenileAdult Spawning adult Offspring production Survival and growth Spillover or leaking RESERVE NON-RESERVE Ontogenetic shifts Seeding from reserve Generic model

Conclusions Ontogenetic shifts happen as individuals try to maximize µ/g Shifts happen in habitat selection, reproduction, diet, and behavior Incorporating an understanding of these shifts crucial to effective management and conservation Plasticity in ontogeny is important but not always well understood –Manage for variance, not just the mean