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Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements to Master Fisher – Gerson “Nicky” Martinez
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Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Mar 26, 2015

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Page 1: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands

Barbara L. Kojis, Norman J. Quinn and Liam Carr

Acknowledgements to Master Fisher – Gerson “Nicky” Martinez

Page 2: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Questions addressed by this studyWhat is the status of the mutton snapper spawning

aggregation?What are the some of the life history characteristics

of the St. Croix mutton snapperWhere and when do juvenile mutton snapper recruit

on STX?How accurate were the habitat maps for the Mutton

Snapper Closed Area?What corals and other invertebrates characterize

the habitat?What types and how many fish were found in the

different habitats in the Mutton Snapper Closed Area?

Page 3: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

BackgroundMutton snapper, virgin snapper,

or “sama” (Lutjanus analis) aggregate to spawn around the full moon in the spring in the southwest of St. Croix.

Fishers traditionally targeted the spawning aggregation at night using handlines.

Catches could be high - a fisher might harvest over 100 mutton snapper in a single night.

Loss of a Nassau grouper spawning aggregation on St. Thomas focused fisher and management authority attention on protecting spawning aggregations.

Local and federal agencies became concerned about the loss of the mutton snapper aggregation to fishing and implemented regulations to protect it.

Page 4: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Mutton Snapper Spawning Aggregation Protected

The Mutton Snapper Seasonal Closed Area was established in 1993 by the Department of Commerce on the recommendation of the CFMC and 1994 by US VI government.

All harvest of fish within the closed area was prohibited from 1 Mar – 30 Jun each year

Mutton Snapper Closed Area

Page 5: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Further protection of the spawning aggregation

Problems with Closed Area Enforcement of the closed area

was difficult because the site was offshore and fishing occurred at night.

Some fishers continued to fish within the closed area during the closure.

Fishers also likely legally fished the aggregation by fishing just outside the closed area.

Mutton snapper seasonal closure implemented

Enacted 2005 (federal waters) and 2006 (territorial waters).

Prohibits harvest and possession of mutton snapper and lane snapper from 1 April – 30 June each year.

Mutton Snapper Closed Area

Page 6: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

What is the status of the mutton snapper spawning aggregation protected by the CFMC and the VI Government?

Can mutton snapper still be caught at traditional fishing sites in the closed area?

What is the catch per unit effort at traditional fishing sites during the presumed peak spawning period – when the seasonal closure is in effect?

Where do mutton snapper aggregate to spawn? How many and what size are the fish in the

aggregation?

Page 7: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Fished within the MSCA to confirm the existence of the spawning aggregation and to obtain CPUE

Relied on expert fishers who knew the best techniques for catching mutton snapper and knew where and when to catch them inside the Mutton Snapper Closed Area (MSCA).

Fished the aggregation during April, May and June before and after the full moon using 50 – 100 lb line, generally without any weights, with single hooks and round robin (scad) for bait. Also, chummed periodically.

Fishing usually commenced at sunset and continued for 4 – 6 hrs or until coolers were full or quota was met.

Gerson “Nicky” Martinez

Page 8: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Success ! Expert fishers Maximiliano Valasquez and Liam

Carr

Page 9: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Catch per Unit Effort (CPUE) – Mutton Snapper (MS) and all fish caught

Page 10: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Diving fishing sites to detect mutton snapper

•Fishing boat anchored at fishing site in late afternoon.•Divers dived from boat just before and at dusk in April, May and June to search for spawning aggregations.•A maximum of one or two mutton snapper were seen on each dive. On most dives no mutton snapper were seen.•Visibility in 2009 was poor – Orinoco River Plume reached STX•No spawning aggregations of mutton snapper seen.

Page 11: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Dedicated mutton snapper searches

In 2009 and 2010, we dived the outer third of the shelf – within and adjacent to the Mutton Snapper Closed Area in May and June 2009 and May, June and July 2010. Diving was conducted in the mid to late afternoon primarily 1 – 5 days after full moon, the time of day mutton snapper spawned in Belize.

None to a few mutton snapper were seen on the dives.

Page 12: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Possible reasons for not finding the aggregation.

Mutton snapper aggregation forms only later in the lunar month.

The aggregation forms in deepwater off the shelf . However, we dived to a depth of at least 95 ft and could see large fish to depths of at least 150 ft. So this is unlikely.

Aggregation forms outside the Mutton Snapper Closed Area – most likely scenario. We visited a site that Martinez showed

us that had large aggregations of fish of different species and which was geomorphologically similar to other known snapper spawning sites.

Martinez had seen mutton snapper aggregating at this site in the past and he saw mutton snapper aggregating in the distance when we visited the site.

Page 13: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

What is the reproductive status of the fish we caught?

Fish were measured, weighed, and gonads removed, identified as to sex, and weighed.

Page 14: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

What was the ratio of males to females caught in the MSCA?

Sex ratio: 2.3 males to 1 female

Month Male Female Sex RatioApril 2 3 0.7May 43 16 2.7June 21 10 2.0Total 66 29 2.3

Table 1.2 Ratio of number of male to number of female Lutjanus analis caught in Mutton Snapper Seasonal Closed Area during the area and seasonal closures in 2009.

Page 15: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Sizes of female and male fish Sizes of female and male fish caught in the Mutton Snapper caught in the Mutton Snapper Closed AreaClosed Area

• The total size range of males and females was similar.

• Males had a higher proportion of small individuals to large.

• Females had a larger proportion of large individuals.

• Size at Lm50 (50% of fish are reproductive) was approximately 39 cm.

• Females appear to mature at a larger size than males.

• Reproductive females ranged in size from 39.3 – 63.5 cm

• Males from 36.7 – 66 cm.

Page 16: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Reproductive Index – Gonad Somatic IndexRatio of gonad weight to total fish weight

Mean gonad somatic index (GSI) (gonad weight (g)*100/weight of fish (g)) with Standard Error bars.

Page 17: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Mutton snapper are batch spawners

Confirmed by size distribution of eggs in ovaries

Page 18: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Evidence for batch spawning in mutton snapperSample of eggs from an ovary showing size range of eggs.

No hydrated eggs were observed.

Size distribution of eggs from fish caught 11 May 09.

Page 19: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

What does batch spawning mean?Batch spawners release eggs in batches over a

period of days or months with only a portion of the yolked eggs spawned in each batch

The fish can release eggs over a number of days during just one month of the spawning period.

Or a fish may release eggs over a number of days each month and/or over several months of the spawning period.

We know that mutton snapper are batch spawners, we don’t know if an individual fish spawns in only one month of the spawning period or for more than one month.

Page 20: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Why is this important?If we want to estimate the size of the spawning

population from counts of fish, we need to know the annual frequency of spawning.

Do fish spawn only in one month each year? Then we can count fish each month in the spawning aggregation

and add up all the months to estimate the number of reproductive fish aggregating at that location.

Do individual fish spawn every month during the spawning season?Then we can count the fish during a single aggregation event

and that should represent all the fish spawning at that aggregation site.

However, it may be more complicated. Is there a size relationship that influences the number of months a fish

spawns? Do large fish spawn more months than small fish? Do small fish only spawn once?

We can use the sex ratio of catches from the aggregation to estimate the size of the female population.

Page 21: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Status of aggregation

Fishing CPUE and analysis of gonads indicate that reproductively mature fish are still migrating to the SW of STX presumably to aggregate to spawn in the area.

Observation of a spawning aggregation of mutton snapper at a reef outside the MSCA suggests that the fish are aggregating outside the closed area.

The maximum size fish caught was 66 cm for males and 63.5 cm for females. Mutton snapper grow to at around 90 cm (SCRFA website).

The maximum weight of the fish we caught was 5.85 kg for females and 5.73 kg for males. Mutton snapper can grow to 15 kg (SCRFA website).

Our sample size was small (127 fish) but it appears that large fish are missing from the spawning population.

• Because we didn’t find the aggregation we don’t know the size of the aggregation.

Page 22: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Genetic analysis of mutton snapper from SW St. Croix (Gold

pers. Com.)

Tissue samples of mutton snapper caught from April – June 2009 were provided to John Gold of Texas A & M University for genetic analysis.

He looked at the effective population size of mutton snapper at different locations.

Effective population size (Ne) is defined as the average number of individuals in a population that actually contribute genes to succeeding generations.

He found that the effective population size of mutton snapper on STX Ne or 341 was below 500 or greater. This is the size needed to maintain adequate genetic variability in the population.

SITE Ne

LOWER

95% CI

UPPER

95% CI

St. Croix 341 314 372

St. Thomas

922 847 1007

PR-East 828 766 896

PR West 646 607 689

Florida Keys

1066

987 1155Mutton snapper aggregation on STX is on the leeward side of the island. Leeward island sites tend to retain larvae and have less larval immigration from other sites.

Limited larval immigration into St. Croix waters from outside could impede recovery if the spawning aggregation becomes depleted.

Page 23: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Where are the juvenile mutton snapper

What habitats do the mutton snapper juvenile recruit to on St. Croix?

Page 24: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Are mutton snapper juveniles found in the backreef embayments in the East End Marine Park?

Page 25: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Juvenile lane, mahogony, yellowtail and schoolmaster snapper were observed in Chenay Bay and Robin Bay. No mutton snapper juveniles

A few mutton snapper recorded in studies by Mateo and Tobias 2001 & 2004 and Adams and Ebersole 2002.

Page 26: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

Large schools of snapper, primarily lane snapper were found in eroded beachrock habitat south of Frederiksted. No mutton snapper seen.

St. Thomas – rocky shoreline

Mutton snapper juvenile – Jan 2011

Lane snapper juvenile – Jun 2011

July 2010 - Frederiksted

Page 27: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

ConclusionThe mutton snapper closed season which prohibits

the harvest and possession of mutton snapper needs to remain in effect while the aggregation rebuilds.Compliance with regulations appears to be very good.Enforcement is much easier because it can be done on

land.Mutton snapper likely do not aggregate within the

closed area. Reverting to just the closed area will not protect the mutton snapper spawning aggregation.

It protects any other mutton snapper aggregation on STX.

The aggregation should be found and monitored on a regular basis.

Page 28: Status of a Mutton Snapper (Lutjanis analis) Spawning Aggregation off St. Croix, U.S. Virgin Islands Barbara L. Kojis, Norman J. Quinn and Liam Carr Acknowledgements.

ACKNOWLEDGEMENTSWe relied heavily on the fishing knowledge of Gerson Martinez and Maximiliano Valasquez.

We could not have accomplished this work without the competent boat handling, diving, and marine safety skills of Captain Gerson Martinez and Salvadore Martinez – Corcino.

We would also like to thank Nicky Martinez, Jr. for his assistance on the boat and expert fishers: Carlos Farchette, and Edward Schuster.

Funding from Caribbean Fisheries Management Council / Coral Reef Conservation Grant Program

Division of Fish and Wildlife and NOAA NMFS are gratefully acknowledged for the research permit.