Eastern Tropical Pacific Ocean | Dolphinfish Research Program | Mahi-Mahi | Mahi | Dorado | Dolphin | Dolphinfish
mahi mahi, dolphinfish, dolphin, dorado, fisheries, FADs, tag and release
mahi mahi, dolphinfish, dolphin, dorado, fisheries, FADs, tag and release
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Eastern Tropical Pacific Ocean

Tropic Star Lodge DRP Research Updates

Dolphinfish Habitat Use off Tropic Star Lodge

By Dr. Wessley Merten – November 2020

 

 

Between the Western Central Atlantic Ocean (WCA), where our tagging program has been active since 2002, and the Eastern Pacific Ocean (EPO), where our program expanded with funding provided by the Guy Harvey Ocean Foundation two years ago, there are stark contrasts in oceanography, environmental variability, and pelagic habitat.  Last year, with field work based out of Tropic Star Lodge, we began to investigate how adult male and female dolphinfish vertical movement patterns off Panama compare to data collected on dolphinfish in the WCA since 2005. Many factors, including the productivity of surface waters, patterns of upwelling, the presence and absence of shallow oxygen minimum layers and differences in temperature, ocean currents, and the existence of holopelagic algae may influence differences in how adult dolphinfish behave between these two oceans.  All are observations that have never been concurrently documented for this species. Important to better describing the ecological niche that dolphinfish occupy and how vertical movement constraints or strategies could expose fish to differing rates of fishing mortality between these oceans, results can aid fishery managers in better predicting how dolphinfish may be exposed to different fishing gear types based on the prevailing oceanographic and environmental conditions. Using a thread-through satellite tag method, we acquired a 26-day and 30-day (full interval) record for a 39″ bull and 45″ cow, respectively, last November. The fish were caught aboard Miss Puerto Rico and Miss South Africa. They were tagged and released on two consecutive days during last year’s tagging trip approximately 20 miles west-southwest of TSL. While this work is certainly exciting on the water (see highlights from last November’s tagging trip in the video below), data analysis

FIGURE 1 FREQUENCY SCATTERPLOTS OF RELATIVE MAXIMUM DIVE DEPTH PER DIVE(% OF MAXIMUM DEPTH PER DIVE) BY TIME OF DAY AND TEMPERATURE FOR AN ADULT FEMALE (LEFT) AND MALE (RIGHT) DOLPHINFISH TRACKED OFF PANAMA FOR 30 AND 23 DAYS, RESPECTIVELY.

and advancing scientific knowledge of this species to conserve it for generations to come is our driving force. Upon initial comparison of maximum depth per dive for both fish, habitat use appeared limited in scale. The vast majority of all dives were between 20% and 40% of the maximum depth visited for both fish (96.8 and 125.1 meters) and the female exhibited a less structured diving pattern than the male, which repeatedly and more frequently dove to intermediate depths (30-60 meters).  When compared to records from the WCA, these fish neither expanded their diving behaviors within the vicinity of their maximum dive depths nor engaged in ritualized, more repetitive, diving behaviors during crepuscular and night-time periods. The female, however, did exude some similarities with less deep-diving behavior in the late afternoon followed by increased dive activity during dusk. A special thanks to Collin Glaser, a student at Roger Williams University, for processing tag 175818 as part of his internship with the Beyond Our Shores Foundation this past semester.

FIGURE 2 - FREQUENCY SCATTERPLOTS OF RELATIVE MAXIMUM DIVE DEPTH PER DIVE (% OF MAXIMUM DEPTH PER DIVE) BY TIME OF DAY AND TEMPERATURE FOR DOLPHINFISH TRACKED IN THE WESTERN CENTRAL ATLANTIC OCEAN (BLACK BOX - UPPER PANEL) AND EASTERN PACIFIC OCEAN (BLUE BOX - LOWER PANEL).

Return Migrants and Satellite Tags Surface

By Dr. Wessley Merten – March 2020

 

 

In November 2018, the Beyond Our Shores Foundation (BOSF) began work to expand the Dolphinfish Research Program (DRP) to the Tropic Star Lodge

(TSL) in southwestern Panama.  This work continues today and is funded in part by the Guy Harvey Ocean Foundation (GHOF).  Through mid-March 2020, a total of 500 dolphin have been tagged and released by 21 vessels and approximately 154 anglers.  This effort has led to the recovery of 14 dolphinfish in the Eastern Pacific Ocean (EPO) and the deployment of eight pop-up satellite archival transmitters.  We recently received three recaptures reported by Captain Fernando Brias of Dios Primero, an artisanal fishermen based out of San Miguel Bay, that provided the first evidence of annual residents in Panama.  In a recent longline set, three fish had tags, and of those, two were fish that were tagged and released by Miss Puerto Rico and Miss England off Piñas Bay, Panama, in January 2019.

FIGURE 1 – QUANTITATIVE (LEFT) AND QUALITATIVE (RIGHT) MOVEMENT DYNAMICS OF DOLPHINFISH IN THE EASTERN TROPICAL PACIFIC OCEAN.  NUMBERS INDICATE DAYS AT LIBERTY.  TWO DOLPHINFISH WERE RECENTLY RECOVERED OVER PANAMA’S CONTINENTAL SHELF AFTER 391 AND 403 DAYS AT LIBERTY, THE FIRST TWO EXAMPLES OF ANNUAL RESIDENTS IN PANAMA.  IN ADDITION, RECENT SATELLITE TAG DEPLOYMENTS (BLUE ARROWS) REVEALED LARGE SOUTHERLY MOVEMENTS INTO COLUMBIAN WATERS IN 26 AND 30 DAYS.  TSL=TROPIC STAR LODGE; CO=COLUMBIA; PA=PANAMA; HS=HIGH SEAS; PT=PLAYA TAMBOR, COSTA RICA; PA=PUNTA ARENAS, COSTA RICA; GC=GULF OF CHIRIQUI.

While we do not know whether these fish remained in Panamanian waters for their entire time at liberty (resident substock?), these events could be the first evidence of annual return migrants to the region.  The question then becomes, where did they go?  Of the other conventional recoveries obtained, four were fish that were recaptured west-northwest of Panama.  As for satellite tag deployments, recent movements showed west-southwest to nearly southerly dispersals into Columbian waters.  After only 15 months of research funded by the Guy Harvey Ocean Foundation, we are beginning to acquire fascinating examples of the movements and life history patterns of dolphinfish in the EPO.  Stay tuned for our next update that will examine the vertical movement strategy of the bull and cow that moved south into Columbian waters.

FIGURE 2 – QUANTITATIVE MOVEMENT DYNAMICS OF DOLPHINFISH OFF PIÑAS BAY, PANAMA. NUMBERS INDICATE DAYS AT LIBERTY. THE UNLABELED RED OVAL IN THE CLUSTER OF YELLOW OVALS (RELEASES) WAS A FISH RECAPTURED AFTER 56 DAYS AT LIBERTY. BLUE= SATELLITE TAG MOVEMENTS; RED= CONVENTIONAL MOVEMENTS. A COMMA INDICATES MULTIPLE FISH RECAPTURED IN A LONGLINE SET.

First Year of Research Complete

By Dr. Wessley Merten – December 2019

 

 

It has been a year since the Dolphinfish Research Program expanded to the Tropic Star Lodge located in Pinas Bay, Panama. Recently, with support from the Guy Harvey Ocean Foundation and the Guy Harvey Research Institute, we embarked on our second research expedition to continue working with the Captains, mates, and visiting anglers at TSL to implement a robust tagging program in their waters. Below are some updates regarding our progress to date.

 

Total reported releases from 11.24.2018 to 11.24.2019: 447
# of Outings with reported releases: 101
Average size tagged: 30.96″ through 11.24.19
Largest fish tagged: 59″ (Record: Mr. Steve Roden)
Smallest fish tagged: 15″ (Record: Captain Fidel)
Most tagged in a single outing: 21 – Miss South Africa 11.27.18
PSAT movements: 6 records acquired – total monitoring time 33.69 days Longest single record 12.29 days.

 

Conventional Recaptures: 8 with a 1.8% recapture rate
Maximum conventional tag days at liberty = 96
Longest conventional tag movement = 796 mi. WNW caught by VZ purse seiner (Tagged by Miss Skandia) (oceanic and coastal stock mixing) (see article below)
Longest satellite tag movement = 168 mi W pop-off after 13 days
Maximum days at liberty for return migrant off Pinas Bay = 56

 

A total of 9 vessels at TSL have had fish recaptured or helped with a PSAT deployment.

Major Dolphin Recovery in the Eastern Pacific Ocean –

 

By Dr. Wessley Merten – September 2019

 

For a species as important as dolphin to so many fishing sectors in the Atlantic Ocean, one would think that we would know the status of the health of the population in the region.  Unfortunately, neither the National Oceanic and Atmospheric Administration (NOAA) nor any of the international fisheries management agencies in the Atlantic (e.g., International Commission for the Conservation of Atlantic Tunas (ICCAT) or Caribbean Regional Fisheries Mechanism (CRFM)) have made it a priority to conduct a modern stock assessment on the species.  The only modern stock assessment on dolphin was conducted by the Inter-American Tropical Tuna Commission (IATTC) which we reported about in our May 2018 newsletter.  Tropic Star Lodge (TSL).  This research is one component of GHOF’s

Eastern Tropical Pacific Seascape (ETPS) project which is a partnership between GHOF, the Guy Harvey Research InstituteNova Southeastern University and TSL.  The objective of the ETPS project is to tag and collect migratory data from 3 species of billfish (sailfish, blue and black marlin) in the Pacific Ocean in order to shed light on the differences between the habitat use of the 3 species.  In addition, the project aims to collect migratory data on sharks, rooster fish, and dolphinfish.  In terms of dolphinfish and our involvement in the ETPS project, through the end of August 2019, a total of 381 dolphin have been tagged and released, of which 9 have been recovered.  Our most recent recovery reported by Pablo Luis Suarez and Gastelum Zuñiga Mario Francisco (Figure 1 – above) shows that large individuals of the purported resident coastal sub-stock in Panama can mix with the oceanic sub-stock in the high seas.  This is the first quantified evidence of these dynamics.  Mr. Suarez and Mr. Francisco caught the fish aboard a Venezuelan flagged purse seiner M/N Taurus-1 while fishing in the high seas of the EPO.  M/N Taurus-1 was targeting tuna when the dolphin was caught.  In addition to acknowledging Mr. Suarez and Mr. Francisco for reporting the recovery, we would like to thank IATTC and Marlon Roman in particular for sending us the tag that was recovered on the fish.  We would also like to congratulate Captain Mosquera of Miss Skandia of the Tropic Star Lodge for tagging and releasing this bull in January 2019.  For more information on other movements recorded to date (Figure – article below) offshore TSL, in the Gulf of Panama, or along the continental shelf break from northwestern Panama to Costa Rica, click here to read a brief but detailed article.  To help the DRP send kits to anglers from southern California to Manta, Ecuador, and to expand throughout the eastern tropical Pacific Ocean consider making a donation today.  Click here to donate to DRP expansion in the Pacific.

 

 

Tropic Star Lodge Dolphinfish Research Program Update –

 

 

By Dr. Wessley Merten – February 2019

Expansion to the Tropic Star Lodge –

 

By Dr. Wessley Merten – December 2018

 

Built in 1963, the Tropic Star Lodge has a rich history and exemplary reputation as one of the best fishing destinations in the world.   The Tropic Star Lodge has provided the ultimate experience for Dolphinfish Research Program and the Tropic Star Lodge, Guy Harvey Ocean Foundation, Guy Harvey Research Institute, NOVA Southeastern Universityoffshore and inshore fishermen for more than 50 years and is very active in fisheries conservation work.  The Tropic Star Lodge was not only the first fishing resort in Panama to begin releasing all roosterfish and cubera snapper but it also adopted the use of circle hooks in the early 90s to improve the survival rates of released fish. Tropic Star Lodge, along with many leaders in Panama, have been responsible for establishing a 20-mile non-commercial fishing zone around Piñas Bay and also a decree that protects all billfish and roosterfish from commercial harvest.    Click here to read a document prepared by Panama’s Authority in Aquatic Resources.  Many of the topics discussed and progress explained in that document are the result of years of work with many different entities including the Tropic Star Lodge.

Dorado satellite tracking begins off southwest Panama Dolphinfish Research Program
JESSICA HARVEY, OF THE GUY HARVEY OCEAN FOUNDATION, AND RYAN LOGAN, PH.D. STUDENT AT THE GUY HARVEY RESEARCH INSTITUTE AT NOVA SOUTHEASTERN UNIVERSITY, PASS A 39.5″ BULL FITTED WITH A POP-UP SATELLITE ARCHIVAL TAG (PSAT) NESTLED IN A SLING TO A DIVER IN THE WATER DURING THE 2018 TROPIC STAR BILLFISH TOURNAMENT. THE BULL SHOT OUT OF THE SLING FULL OF LIFE AND SIGNIFIED THE BEGINNING OF SATELLITE TRACKING WORK FOR DORADO OFF THE SOUTHWEST COAST OF PANAMA WITH OPERATIONS BASED OUT OF THE TROPIC STAR LODGE. THE BULL WAS CAUGHT BY LOUISA GIBSON OF THE GUY HARVEY OCEAN FOUNDATION. PHOTO: WESS MERTEN 

The tremendous conservation efforts outlined in the document above are fantastic achievements for Panama and we are pleased to announce that through the support of the Tropic Star LodgeGuy Harvey Research Institute at NOVA Southeastern UniversityGuy Harvey Ocean Foundation, and captains, mates, local and visiting fishermen in Panama, the Dolphinfish Research Program successfully expanded to southwest Panama during the 2018 Tropic Star Billfish Tournament.  We outfitted the lodge’s fleet of Bertrams, along with 4 private boats, with more than 1100 conventional tags and we began our satellite tracking and fishing fleet work.   We are extremely excited to get the Tropic Star Lodge involved in the Dolphinfish Research Program to help advance ocean conservation and our knowledge of the life history, movements, population dynamics of dolphinfish in Panama.

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