The grunion were running last weekend, so I went down to the Venice Beach breakwater just before midnight to watch them mate. The sight of thousands of slim, silvery fish wiggling desperately out of the surf and struggling to spawn before the next wave crashed upon them made me think, of course, of those birthright Israel trips.

This summer, a record 23,500 participants are expected to visit Israel as part of TAGLIT-birthright Israel. The program offers free 10-day tours of Israel for Jewish young adults, 18 to 26. This year, the organization received nearly 32,000 applications — also a record high.

Part of the success is undoubtedly the attraction of all-expense-paid foreign travel. When I was in college the simple words “free trip” would have had me packed and ready to go to Jonestown without thinking twice.

But birthright’s success is more genuine: it combines education and spirituality with a search for roots and meaning, and anchors the whole experience in a 10-day nonstop party.

It’s no wonder that birthright, founded seven years ago by philanthropists Michael Steinhardt and Charles Bronfman, can count as one of the few unmitigated successes the Jewish establishment has had in involving younger Jews in Jewish life.

Since 2000, the program, jointly funded by private philanthropists, the Jewish Agency for Israel, the Israeli government and the North American federation system, has sent more than 120,000 young Jews from 51 countries to Israel for free.

But let’s be honest about what accounts for a good part of the program’s runaway success — hormones.

“No one tells you it’s about hooking up with other Jews,” one 20-something participant told me, “but there’s plenty there to make it happen.”

There is no curfew, chaperones who are in some cases only a couple of years older than the visitors and lots of booze.

“What happens among the Diaspora,” one happy birthrighter from Pittsburgh told me, “stays among the Diaspora.”

Which is why I’m not quoting anyone by name here.

One 21-year-old UC San Diego sophomore I spoke with said the subtext wasn’t that hidden. Her Israeli organizer told the group the best thing about birthright and Israel is that they could hitch up with other Jews and make Jewish babies. She recounted his exact words in a thick Israeli accent: “When you see a cutie on the beach in Tel Aviv and you say, ‘Hey, what’s cooking?’ you know you’re talking to a Jew.'”

Her friend, a young man who also attends UC San Diego, said the message wasn’t covert, and it didn’t bother him at all.

“I was fine with it,” he said. “We get to go on this great trip, and they get to tell us what they want.”

The message, he said, is that you need to make Jewish babies, because Jewish babies will save the Jewish people. If birthrighters needed any more nudging, each trip culminates in a kind of mega-meet-up. Held in Jerusalem, it brings every birthright group together in an amphitheater in Jerusalem, the Holy City, where they hear some great rock music, then adjourn into a raucous, beer-fueled party. (The party is free, the beer you pay for).

“I faked an Israeli accent to hit on girls,” another birthrighter told me. “It works better.”

Again, I think of the grunion. If you haven’t seen them, it’s worth grabbing a warm coat and a thermos of mint tea and heading down to the beach during mating season, which occurs between May and September during the full and new moon.

The fish, which are relatives of smelt, ride the waves onto shore. The females use their tails to wriggle down until only their heads, bug-eyed and vulnerable, poke from the sand. Into this nest, they squeeze their eggs.

Meanwhile the males find females to squirm around, and in a frenzied swarm release their milt. The murky liquid slides down the females’ backs and onto the eggs. Some females deposit eggs though no males surround them — but I’m sure there’s a guy for them on some other beach.

Two weeks later the fertilized eggs, hidden under the feet of countless sunbathers and sea gulls, hatch, and a new generation of grunion swarm the tides.

It’s remarkable — the utter implausibility of fish finding one another on dry land, the rush to hook up, the race to meet and secrete. That there are still grunion in the world is nothing short of miraculous — and one could say the same of the relatively few Jews who manage, against the odds of persecution and assimilation, to reproduce. If the alcohol-fueled all night hotel room parties that our philanthropic dollars support help, who’s to quibble? If the birthright mega-gathering is closer to a grunion run at low tide than a Zionist congress, so what?

Like most Jews in a generation that missed out on the birthright junket, I’m jealous, but supportive. I understand that, as my friend Jon Drucker is fond of saying, Jewish survival is not in the genes, but in the jeans.

But I do wonder if the message is getting through that there is more to Jewish survival than hooking up. The rabbis teach that all the Jewish souls that ever were, were present at Sinai. But us plodding literalists would argue that it is the unerring emphasis on Jewish values — or rather, the debate over those values — and on Jewish deeds, or mitzvot, that determine, truly, how many Jews there are in this world.

Two Jews can create such a person, but a non-Jew can become that person too.

For ultimately, unlike grunion, Jewish souls are made, not spawned.

New video of Taglit-birthright trip. Contains no spawning